Simulink.VariantVariable Class

R2026b

Namespace: Simulink

Create variant parameter object

Description

Use the Simulink.VariantVariable class to create a variant parameter object. Variant parameter objects enable you to vary the values of block parameters in a Simulink^® model conditionally. For an overview of variant parameters, see Use Variant Parameters to Reuse Block Parameters with Different Values.

You can specify multiple values for a variant parameter object and also set properties such as data type and dimensions applicable to all the choice values. Each value of the variant parameter object is associated with a variant condition expression. After creating the object, use it to set the value of block parameters in a model, such as the Gain parameter of a Gain block. During simulation, the value associated with the variant condition that evaluates to true becomes the active value for that parameter. The values associated with the conditions that evaluate to false become inactive.

Before you create a new Simulink.VariantVariable object, create a Simulink.VariantControl object representing the variant control variable to be used in the Simulink.VariantVariable object. Use these variant control variables to specify the variant condition expression associated with each choice value of a variant parameter, for example, 'V == 1' where V is a Simulink.VariantControl object. The Simulink.VariantControl object allows you to specify an ActivationTime for the variant parameter and a Value that is used to evaluate the variant conditions and determine the active choice of the variant parameter. For examples on usage of each type of variant control value, see Use Variant Control Variables in Variant Parameters.

Note

• You create a variant parameter object and its variant controls programmatically in the base workspace, model workspace, mask initialization code of a masked block, or in the Design Data section of a Simulink data dictionary. For workspaces and data dictionaries, you can also use the Add menu in the Model Explorer. To edit a variant parameter object, double-click the object from the workspace or data dictionary to open the Simulink.VariantVariable dialog box.

• Variant Legend does not display the variant conditions for variant parameters. Use the Variant Parameters tab in the Variant Manager window to view and manage the variant parameters present in the workspaces associated with the model. See Manage Variant Parameters Using Variant Manager (Simulink Variant Manager).

• For variant parameters with startup activation time, you can use a Parameter Writer block to initialize the associated Simulink.VariantControl object. For an example, see Initialize Variant Control Value of Variant Parameter Using Parameter Writer Block.

• For variant parameters with runtime activation time, you can use a Parameter Writer block or the setVariable function of a Simulation object to update the Simulink.VariantControl object during simulation or execution of the generated code. For more information, see Change Active Choice of Variant Parameters and Variant Parameter Banks During Simulation or Execution of Generated Code.

Creation

P = Simulink.VariantVariable creates an empty variant parameter object.

P = Simulink.VariantVariable(PropertyName=Value) creates a variant parameter object and sets Properties using one or more name-value arguments. Use this syntax to specify multiple values for the object and to associate each value with a variant condition expression. You can also specify other properties of the object such as data type, storage class, and dimension.

Properties

Choices — Variant conditions and values

cell array

Variant conditions and values, specified as a cell array. During simulation, when a variant condition evaluates to true, its associated value becomes active. When a variant condition evaluates to false, its associated value becomes inactive. No two values of the same variant parameter can be associated with the same variant condition.

You can specify the variant conditions as boolean MATLAB^® expressions. For information on the supported operators and operands, see Variant Control Mode in Variant Parameters.

The value of a choice of a variant parameter can be one of these types:

• Numeric value

• Name of a Simulink.Parameter object

• Name of a Simulink.Parameter object or an object of a class that inherits from Simulink.Parameter, with the value of the object set to a mathematical expression specified using the slexpr function.

Arithmetic and logical operations on a variant parameter object applies the operation on the active choice value. For example, p + 2 adds 2 to the active choice value of p.

You can specify one of the choice values as a default value for the variant parameter by setting its variant condition to the (default) keyword. Simulink uses the default value for the variant parameter when none of the other variant conditions evaluate to true.

Example: P = Simulink.VariantVariable('Choices',{'V == 1',4.5,'V == 2',9.5})

Example: P = Simulink.VariantVariable('Choices',{'V == 1',3,'(default)',6})

Example: slparam_1 = Simulink.Parameter(slexpr("a_vp+b_vp")); slparam_2 = Simulink.Parameter(slexpr("a_vp-b_vp")); vp_tunable = Simulink.VariantVariable('Choices', {'vc_startup==1','slparam_1','vc_startup==2','slparam_2'})

Attributes:

GetAccess	private
SetAccess	private

Specification — Properties of variant parameter object

Simulink.Parameter object name

Properties of variant parameter object such as data type and storage class applicable to all the choice values, specified as a Simulink.Parameter object.

The following considerations apply when configuring the Specification property:

• If the Specification object has nonzero dimensions, and the activation time of the variant parameter is set to update diagram, the dimension of the active choice must match the dimension of the specification object. For other activation times, all choices must have dimensions that match the specification object. For code compile activation time, if the variant parameter values have variable dimensions, the dimension of the Specification object must be set to [0,0].

• If the Specification object has the Min and Max properties set, and the activation time of the variant parameter is set to update diagram, then the value of the active choice is verified against the specified range. For other activation times, the range check applies to values of all choices.

• When you assign Simulink.Parameter objects as the choices for a variant parameter and also set the Specification property of the variant parameter, Simulink verifies that properties such as DataType and Dimensions of the active Simulink.Parameter choice match those defined in the specification object.

• When using both Specification and Bank properties for a Simulink.VariantVariable object, the specification object must have storage class set to Auto and it must not use symbolic dimensions. For a variant parameter bank, use a Simulink.VariantBankCoderInfo object to specify code generation attributes.

• The default storage class of a Simulink.Parameter object is Auto. If you specify the storage class as Auto, the value of the object is inlined to the literal value in the generated code. If you specify the storage class of the object anything other than Auto, the object is represented as tunable parameters using symbolic names in the generated code. For more information, see Options to Represent Variant Parameters in Generated Code (Embedded Coder).

Example: P = Simulink.VariantVariable('Specification','sp','Choices',{'V == 1',2,'V == 2',3});

Attributes:

GetAccess	public
SetAccess	public

Bank — Name of variant parameter bank

'' (default) | string scalar | character vector

Name of variant parameter bank (Simulink.VariantBank) object, specified as a string scalar or character vector.

With Embedded Coder^®, you can group variant parameters in the generated code by adding them to the same variant parameter bank. The variant parameters must have activation time set to startup or runtime and must have the same set of variant conditions. Use the Simulink.VariantBank class to create a variant parameter bank object and set the Bank property of the Simulink.VariantVariable object to the name of the variant parameter bank. For more information, see Simulink.VariantBank.

Example: P = Simulink.VariantVariable('Bank','ParamBank','Choices',{'V == 1',2,'V == 2',3});

Attributes:

GetAccess	public
SetAccess	public

Data Types: string | char

Methods

Public Methods

addChoice	Add choices to variant parameter object
getChoice	Return choices of variant parameter object
setChoice	Modify existing choices of variant parameter object
removeChoice	Remove choices from variant parameter object

Specialized Operators and Functions

These methods specialize standard MATLAB operators and functions for objects in this class.

bitcmp	Performs bit-wise complement on input.
eq	Determines whether the inputs are equal.
gt	Determines whether the first input is greater than the second input.
mrdivide	Divides the first input by the second input.
or	Performs a logical OR on inputs.
uminus	Negates the input.
bitor	Performs bit-wise OR on inputs.
ge	Determines whether the first input is greater than or equal to the second input.
le	Determines whether the first input is less than or equal to the second input.
mtimes	Multiplies the inputs.
plus	Adds the inputs.
uplus	Returns the value of the input.
and	Performs logical AND on inputs.
bitshift	Shift bits by specified number of places.
lt	Determines whether the first input is less than the second input.
ne	Determines whether the inputs are not equal.
bitand	Performs bit-wise AND on inputs.
bitxor	Performs bit-wise XOR on inputs.
minus	Subtracts the second input from the first input.
not	Returns logical NOT of input.

Examples

Create Variant Parameters Programmatically Using Simulink.VariantVariable Class

This example shows you how to create variant parameters using the Simulink.VariantVariable class in the base workspace. To create the variant control and variant parameter objects in a data dictionary, see Add Entry to Design Data Section of Data Dictionary. To create the objects in model workspace, see Change Model Workspace Data.

Create Variant Parameter

In the MATLAB® Command Window, define a variant control variable V using the Simulink.VariantControl class and set its value to 1. The default variant activation time for the variant control is update diagram.

V = Simulink.VariantControl('Value',1);

Create a variant parameter object by specifying the variant conditions and values for the choices.

Use V to specify a variant condition for each choice of the variant parameter. During simulation, the choice value that corresponds to the variant condition that evaluates to true becomes the active value of the parameter. Thus, the variant control V allows you to set one of the choice values as the active variant.

Since the value of V is 1, the condition V == 1 evaluates to true when you simulate the model and hence K1 is assigned a value of 3.5.

K1 = Simulink.VariantVariable('Choices',{'V == 1',3.5,'V == 2',8.3});

You can perform arithmetic and logical operations on the variant parameter object.

P = K1*3;

Specify Default Value for Variant Parameter

To specify one of the choice values as a default value for the parameter, use the (default) keyword for the variant condition. Simulink® uses the default value for the variant parameter when none of the other variant conditions evaluate to true. When activation time is set to code compile, this default value is assigned in the #else condition. When activation time is set to startup, the value is assigned in the else condition in the generated code.

K2 = Simulink.VariantVariable('Choices',{'V == 1',3,'(default)',6});

Analyze Variant Parameter Values for Consistent Signal Attributes

When you specify a variant activation time other than update diagram for the Simulink.VariantControl, Simulink analyzes all choice values of the variant parameters for consistency of signal attributes such as datatype, dimensions, and complexity. Activation time also determines whether the generated code must contain only the active choice or both active and inactive choices.

Create a variant control variable V with variant activation time set to update diagram analyze all choices.

V = Simulink.VariantControl('Value',1,'ActivationTime','update diagram analyze all choices');
K4 = Simulink.VariantVariable('Choices',{'V == 1',int8(3),'V == 2',int8(7)});

If you add the choice value 5.1 to K4 and use K4 in a model, the model compilation fails because the data type of the choice is not of type int8.

K4 = setChoice(K4,{'V == 3',5.1});

Specify Common Code Generation Properties for Variant Parameter Values

If you intend to generate code for a model containing variant parameters, use a Simulink.Parameter object to define specifications such as data type, dimensions, and storage class for all the variant choices.

sp = Simulink.Parameter(int8([])); 
sp.CoderInfo.StorageClass = 'Custom';
sp.CoderInfo.CustomStorageClass = 'Define';
sp.CoderInfo.CustomAttributes.HeaderFile = 'vparam.h';

Define a variant control variable V using the Simulink.VariantControl class.

V = Simulink.VariantControl('Value',1);

Create a variant parameter and set the Specification property. This command defines all the choices to be of type int8 with the specified custom storage class attributes for code generation.

K3 = Simulink.VariantVariable('Specification','sp','Choices',{'V == 1',4,'V == 2',8});

Create Variant Parameter Values with Different Dimensions

The example shows you how to create a variant parameter with choice values of different dimensions. All other attributes, such as data type and complexity, must be the same across all choices. To generate code for variant parameters that have values with different dimensions, use Embedded Coder®. If you set the activation time of the associated Simulink.VariantControl object to code compile, Embedded Coder generates code for both active and inactive values of variant parameters.

In this example, the variant parameter kv1 has values with different dimensions and the variant activation time of the associated variant control variable object V is set to code compile. The storage class of kv1 is set to exported data scope (ExportedGlobal (Embedded Coder)) to generate code that reuses the variant parameter values that you specify. You can choose to generate code that imports variant parameter values and its dimensions from external code prior to code compilation by setting the storage class with imported data scope (ImportedExtern, ImportedExternPointer (Embedded Coder)).

% Variant parameter specification
spec = Simulink.Parameter();
spec.CoderInfo.StorageClass = 'ExportedGlobal';

% variant control variable
V = Simulink.VariantControl('Value',1,'ActivationTime','code compile');
 
% variant parameter 
choice1 = 'V == 1';
choice2 = 'V == 2';
choice3 = 'V == 3';
kv1 = Simulink.VariantVariable('Choices',...
    {choice1,[1, 2, 3, 4],choice2,[1, 2, 3, 4, 5],choice3,[1, 2, 3, 4, 5, 6]},...
    'Specification','spec');

When you generate code for a model that uses kv1, the code contains active and inactive values of kv1 with dimensions represented as symbols. All values are enclosed in C preprocessor conditionals #if and #elif. When you compile the code, Simulink® evaluates the preprocessor conditionals and preserves the code only for the active value of the variant parameter. For more information, see Compile Code Conditionally for All Values of Variant Parameters with Same and Different Dimensions (Embedded Coder).

Use Mathematical Expressions as Values of Simulink.VariantControl Objects and Simulink.VariantVariable Choices

Set the value of a Simulink.VariantControl object and the value of a choice of a Simulink.VariantVariable object to mathematical expressions involving literal numbers, MATLAB® variables, or Simulink.Parameter objects. With expressions, you can:

• Express a value as a relationship between known physical constants instead of as an unidentifiable literal number.

• Explicitly model algebraic dependencies between parameter data. When you change the values of independent data, you do not need to remember to adjust the values of dependent data.

To specify a mathematical expression for the value of a Simulink.VariantControl object or the value of a choice of a Simulink.VariantVariable object:

1. Create a Simulink.Parameter object or an object of a class that inherits from Simulink.Parameter.

2. Set the Value property of the object to the expression by using the slexpr function.

3. Use the object to set the value of the variant control or the values of the choices of a variant parameter.

You can generate C or C++ code that preserves the expressions using Embedded Coder® by applying compatible storage classes. For applicable code generation techniques and considerations, see Code Generation of Parameter Objects with Expression Values (Embedded Coder).

Explore Example

The example model uses a variant parameter object vp_tunable that is used to set the Gain parameter of a Gain block. The model configuration parameter Default parameter behavior for code generation optimization is set to Tunable.

vp_tunable uses a Simulink.VariantControl object vc_startup that has activation time set to startup and ExportedGlobal storage class, which yields a global variable in the generated code. The choices of vp_tunable are Simulink.Parameter objects with values set to mathematical expressions. The values of the parameter objects a_vp, b_vp, a_vc, and b_vc that are used in the expressions are imported from an external file external_imp_defines.h.

% These parameter objects have the CustomStorageClass property set to ImportedDefine
% and HeaderFile property set to 'external_imp_defines.h'.
a_vc = Simulink.Parameter(int32(1)); 
b_vc = Simulink.Parameter(int32(2)); 
a_vp = Simulink.Parameter(int32(6));
b_vp = Simulink.Parameter(int32(5));

% This parameter object has the StorageClass property set to 'ExportedGlobal'
vc_slprm = Simulink.Parameter(slexpr("a_vc+b_vc")); 
% Variant control for the vp_tunable parameter
vc_startup = Simulink.VariantControl(Value=vc_slprm,ActivationTime="startup");

% These parameter objects have the CustomStorageClass property set to 'ExportToFile',
% HeaderFile property set to 'varparam.h', and DefinitionFile property set to 'varparam.c'.
slparam_1 = Simulink.Parameter(slexpr("a_vp+b_vp")); 
slparam_2 = Simulink.Parameter(slexpr("a_vp-b_vp")); 
slparam_3 = Simulink.Parameter(slexpr("a_vp*b_vp")); 

vp_tunable = Simulink.VariantVariable(Choices= ...
 {'vc_startup==1','slparam_1','vc_startup==2','slparam_2','(default)','slparam_3'});

This code snippet shows the content of the external file external_imp_defines.h.

#define a_vc    1
#define b_vc    2
#define a_vp    6
#define b_vp    5

With Embedded Coder, you can generate code that defines a global variable and initializes it by using an expression involving system constants.

/* varparam.c */
/* Definition for custom storage class: ExportToFile */
real_T slparam_1 = a_vp+b_vp;
real_T slparam_2 = a_vp-b_vp;
real_T slparam_3 = a_vp*b_vp; 

/* <model>.c */
/* Exported block parameters */
int32_T vc_startup = a_vc+b_vc;  

/* Model initialize function */
 if (vc_startup == 1) {
    mVarParamVCtrlSlexpr_P.vp_tunable = slparam_1;
  } else if (vc_startup == 2) {
    mVarParamVCtrlSlexpr_P.vp_tunable = slparam_2;
  } else {
    mVarParamVCtrlSlexpr_P.vp_tunable = slparam_3;
  }

Similarly, in this model, vp_macro is a variant parameter that uses a Simulink.VariantControl object vc_cc with activation time set to code compile. Both vc_cc and the choices of vp_macro have the Define storage class that yields a macro in the generated code. The values of the parameter objects a_cc, b_cc, a_vp_cc, and b_vp_cc that are used in the expressions are imported from an external file external_imp_defines.h.

% These parameter objects have the CustomStorageClass property set to 'ImportedDefine'
% and HeaderFile property set to 'external_imp_defines.h'
a_cc = Simulink.Parameter(int32(1));
b_cc = Simulink.Parameter(int32(2));
a_vp_cc = Simulink.Parameter(int32(7)); 
b_vp_cc = Simulink.Parameter(int32(4));

% This parameter object has the StorageClass property set to 'Define' 
% and the HeaderFile property set to 'vcc_define.h' 
vc_slprm_cc = Simulink.Parameter(slexpr("a_cc+b_cc")); 
% Variant control for the vp_macro parameter
vc_cc = Simulink.VariantControl(Value=vc_slprm_cc,ActivationTime="code compile");

% These parameter objects have the CustomStorageClass property set to 'Define'
% and the HeaderFile property set to 'varparam.h'
slparam_1_cc = Simulink.Parameter(slexpr("a_vp_cc+b_vp_cc")); 
slparam_2_cc = Simulink.Parameter(slexpr("a_vp_cc-b_vp_cc")); 
slparam_3_cc = Simulink.Parameter(slexpr("a_vp_cc*b_vp_cc")); 

vp_macro = Simulink.VariantVariable(Choices= ...
 {'vc_cc==1', 'slparam_1_cc', 'vc_cc==2', 'slparam_2_cc', '(default)', 'slparam_3_cc'});

This code snippet shows the content of the external file external_imp_defines.h.

#define a_cc    1
#define b_cc    2
#define a_vp_cc 7
#define b_vp_cc 4

For this variant parameter, Embedded Coder generates code that defines a macro whose value is an expression involving other macros.

/* vcc_define.h */
/* Definition for custom storage class: Define */
#define vc_cc  a_cc+b_cc  /* Referenced by: '<Root>/Gain1' */
#endif 

/* varparam.h */
/* Definition for custom storage class: Define */
#define slparam_1_cc  a_vp_cc+b_vp_cc   /* Referenced by: '<Root>/Gain1' */
#define slparam_2_cc  a_vp_cc-b_vp_cc   /* Referenced by: '<Root>/Gain1' */
#define slparam_3_cc  a_vp_cc*b_vp_cc 

/* <model>.c */
/* Model initialize function */
#if vc_cc == 1
  mVarParamVCtrlSlexpr_P.vp_macro = slparam_1_cc;
#elif vc_cc == 2
  mVarParamVCtrlSlexpr_P.vp_macro = slparam_2_cc;
#else
  mVarParamVCtrlSlexpr_P.vp_macro = slparam_3_cc;
#endif

Specify Simulink.Parameter Object as Variant Parameter Value

This example shows you how to specify the values of choices of variant parameters as Simulink.Parameter variables.

In a vehicle system model, consider the scenario where a parameter value needs to vary depending on whether the vehicle is configured as a sedan or a hatchback. To represent these two possible values, create two Simulink.Parameter objects kv_sedan and kv_hatchback. Use these objects to define the variant parameter.

1. Define the Simulink.Parameter objects.

kv_hatchback = Simulink.Parameter(3.5);
kv_sedan = Simulink.Parameter(4.5);
kv_hatchback.CoderInfo.StorageClass = "ImportedExtern";
kv_sedan.CoderInfo.StorageClass = "ImportedExtern";

2. Define a variant control variable.

V = Simulink.VariantControl(Value=VehicleType.Sedan,ActivationTime="startup");

3. Define the variant parameter using the Simulink.Parameter objects. When you use this variant parameter in the model, the value of the variant parameter in simulation and code generation is determined from the values of the Simulink.Parameter objects.

kv = Simulink.VariantVariable(Choices={'V == VehicleType.Hatchback','kv_hatchback', ...
 'V == VehicleType.Sedan','kv_sedan'});

Here, using Simulink.Parameter variables with ImportedExtern storage class allows you to generate code that imports variant parameter values from your existing user-written code. Thus, you can reuse the values that your existing code defines. During code compilation, the generated code and the user-written code is integrated into a single executable. For an example, see Reuse Variant Parameter Values from Handwritten Code Using Simulink.Parameter Variables (Embedded Coder).

Group Variant Parameter Values in Code Using Variant Parameter Bank

This example shows you how to group variant parameters in the generated code by adding them to the same variant parameter bank (Simulink.VariantBank).

Create a variant parameter bank.

EngineParams = Simulink.VariantBank(Name='EngineParams',Description='Engine parameters',...
                                     VariantConditions={'V == EngType.Small','V == EngType.Big'});

Create a variant control variable V using the Simulink.VariantControl class. The Value property of this object allows you to select an active value for a variant parameter and the ActivationTime property allows you to specify a variant activation time. To use variant parameter banks, the activation time must be set to startup or runtime. Use this variable to specify the variant condition expression for the choice values of a variant parameter.

Create two variant parameter objects K1 and K2 and associate them with the variant parameter bank EngineParams.

Use the name of the variant parameter bank to set the Bank property of a Simulink.VariantVariable object. The generated code groups the Simulink.VariantVariable objects that share the same Bank property in the same structure.

V = Simulink.VariantControl(Value=EngType.Small,ActivationTime='startup');
K1 = Simulink.VariantVariable(Choices={'V == EngType.Small',3,'V == EngType.Big',6},Bank='EngineParams');
K2 = Simulink.VariantVariable(Choices={'V == EngType.Small',[3, 6, 9],'V == EngType.Big',[5, 10, 15]},Bank='EngineParams');

To additionally specify code generation properties for a variant parameter bank, use the Simulink.VariantBankCoderInfo class.

Initialize Variant Control Value of Variant Parameter Using Parameter Writer Block

Use a Parameter Writer block within an Initialize Function block to initialize the value of Simulink.VariantControl objects associated with a variant parameter. The variant controls must have their ActivationTime property set to startup or runtime. In this example, the activation time of the variant control is set to startup.

You can use Parameter Writer blocks within an Initialize Function block to initialize the value of Simulink.VariantControl objects associated with a variant parameter (Simulink.VariantVariable object). This setup allows you to assign the variant control value on the model initialize event, thereby initializing the associated variant parameter. The variant controls and the variant parameter must be defined in the base workspace, model workspace, or data dictionaries linked to the model.

This model that implements a counter using a Unit Delay block uses a variant control V to specify the variant conditions for the variant parameter K. The Parameter Writer block inside the Initialize Function block sets the value of V. The Initialize Function block also initializes the Unit Delay block state with the variant parameter K by using a State Writer block.

When generating code for this model with Embedded Coder, the model initialize function initializes the variant control V before the variant parameter K.

/* Model initialize function */
/* ParameterWriter: '<S1>/Parameter Writer' incorporates Constant: '<S1>/Constant1' */
 V = mVariantControlParamWriter_P.Constant1_Value_a;

/* Variant Parameters startup activation time */
  if (V == 1) {
    mVariantControlParamWriter_P.K = 10.0;
  } else if (V == 2) {
    mVariantControlParamWriter_P.K = 20.0;
  } else if (V == 3) {
    mVariantControlParamWriter_P.K = 30.0;
  }
  /* End of ParameterWriter: '<S1>/Parameter Writer' */
  /* StateWriter: '<S1>/State Writer' incorporates Constant: '<S1>/Constant' */
  mVariantControlParamWriter_DW.UnitDelay_DSTATE =
   mVariantControlParamWriter_P.K;

If you set the Default parameter behavior model configuration parameter to Inlined, the generated code assigns the active value of the variant parameter directly in the model_initialize function without enclosing the values in if/elseif/else conditions.

For applicable limitations, see Limitations.

Limitations

• Variant parameters can only be defined in a base workspace, model workspace, mask initialization code of a masked block, or a data dictionary.

• Only the values of the variant parameters change based on the variant condition that evaluates to true. Other properties, such as storage class, data types, and so forth, remain the same irrespective of the variant condition.

• Variant parameters that are part of a variant parameter bank do not support AUTOSAR code generation.

• The Value property of the variant control variable (Simulink.VariantControl), which determines the active value of a variant parameter, must be one of these types:

  • Integer

  • Boolean

  • Enumerated value

  • Simulink.Parameter object with value of type integer, Boolean, enumeration, or a mathematical expression specified using the slexpr function

  • User-defined type that inherits from Simulink.Parameter

• Using the slexpr function or a Simulink.data.Expression object directly to specify a mathematical expression for the value of a choice of a variant parameter or the variant control used by the variant parameter is not supported. Instead, define the value of the variant parameter or the variant control by using a Simulink.Parameter object with its value set to the mathematical expression by using the slexpr function.

• For variant parameters with ActivationTime set to runtime:

  • Multiple Simulink.VariantControl objects in the condition expressions of the variant parameter choices are not supported.

  • Using the variant parameter in a block that has the Execution Order set to First is not supported. Set the execution order to Based on priority.

  • Export-function models are not supported.

  • Multirate models with the EnableMultiTasking model configuration parameter set to "on" are not supported.

• Using a Parameter Writer block to modify the value of the Simulink.VariantControl object used in a Simulink.VariantVariable object is not supported in these scenarios:

  • The Simulink.VariantControl value is modified in multiple Initialize Function blocks.

  • The condition expression of a Simulink.VariantVariable object contains multiple Simulink.VariantControl objects.

  • The Parameter Writer block is connected to a block that uses a Simulink.VariantVariable object. In this case, the Parameter Writer block supports only changing block parameter values.

  • The Simulink.VariantControl object is configured as a model argument.

  • The model is simulated in accelerator or rapid accelerator mode when the Simulink.VariantControl object is defined in the model workspace.

  • The Parameter Writer block is used to modify the value of a Simulink.Parameter object that is used as the value of a Simulink.VariantVariable choice.

  • The Simulink.VariantVariable object is used in an expression that contains multiple variables, for example, K + A where K is a Simulink.VariantVariable object and A is a MATLAB variable.

  • The Simulink.VariantControl object is created in mask initialization code and its value comes from a mask parameter, base workspace variable, or model workspace variable.

• When you define Simulink.VariantVariable objects and its associated Simulink.VariantControl objects in the mask initialization code of a masked block:

  • Specifying the variant activation time as code compile is not supported.

  • Simulink.VariantBank objects are not supported.

  • Simulink.VariantExpression objects are not supported.

  • Simulink.Parameter objects defined in mask initialization must not be used to create a variant control object or variant parameter.

  • The value of the Simulink.VariantControl object must not be an expression.

  • If a mask parameter is used to create a variant control object or variant parameter, the mask parameter must be tunable and its Evaluate property must be set to on.

  • Accelerator, Rapid Accelerator, SIL, and PIL simulation modes are not supported when a model argument passed to a referenced model is used as a mask parameter that defines a variant control, and that variant control determines a variant parameter used as a child block parameter value.

• When you define Simulink.VariantControl and Simulink.VariantVariable objects in the model workspace:

  • The ActivationTime property of the Simulink.VariantControl object must be set to update diagram, update diagram analyze all choices, runtime, or startup.

  • The objects associated with the variant parameter object, such as the Simulink.VariantControl object, the Simulink.Parameter object used to set the Specification property, and any Simulink.Parameter objects used as values of the variant parameter, must be defined in the model workspace along with the parameter.

Tips

For an overview of variant parameter capabilities and supported workflows across the development lifecycle, see Components — Create Models with Parameter Value Variations.

You can manage and activate variant parameters from Variant Manager. See Manage Variant Parameters Using Variant Manager (Simulink Variant Manager).

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

• For variant parameters with activation time set to startup, you can generate code for both active and inactive choices by installing Simulink Coder™ or Embedded Coder.

• For variant parameters with activation time set to code compile:

  • You must install Simulink Coder to generate code for only active values of variant parameters. Generating code using Simulink Coder is supported only if values of a variant parameter have same dimension.

  • You must install Embedded Coder to generate code for both active and inactive values of variant parameters. Generating code using Embedded Coder is supported for variant parameters values having same and different dimensions.

• When you generate code using Embedded Coder, you can group variant parameters that have the same set of variant conditions and with activation time set to startup or runtime into a structure array in the generated code. Use the Simulink.VariantBank class to group variant parameters into a variant parameter bank and use the Simulink.VariantBankCoderInfo class to specify code generation properties for the variant parameter bank.

For more information on code generation with variant parameters, see Options to Represent Variant Parameters in Generated Code (Embedded Coder).

Version History

Introduced in R2021a

R2026b: Use runtime variant activation time with variant parameters and variant parameter banks

Change the active choice of variant parameters and variant parameter banks during simulation or execution of the generated code by setting the ActivationTime property in the associated Simulink.VariantControl object to 'runtime'. For more information, see Change Active Choice of Variant Parameters and Variant Parameter Banks During Simulation or Execution of Generated Code.

R2026b: Generate code with inlined default parameter behavior when a Parameter Writer block initializes the variant control

You can generate code for models where a Parameter Writer block writes to a Simulink.VariantControl object used by variant parameters when you set the Default parameter behavior model configuration parameter to Inlined. The generated code assigns the active value of the variant parameter directly in the model_initialize function. The code does not contain if/elseif/else conditional statements for the variant parameter initialization.

The Simulink.VariantControl object must meet these conditions:

• The ActivationTime property is set to startup.

• The object is defined in the base workspace, data dictionary, or model workspace and is not configured as a model argument.

• For variant controls defined in the base workspace or a data dictionary, the storage class must produce a tunable variable in the generated code. For variant controls defined in the model workspace, only Auto and Model Default storage classes are supported.

This workflow also supports variant parameter banks (Simulink.VariantBank objects).

R2026a: Generate code for model that references protected model containing variant parameters with code compile activation time

You can generate code for a model that includes a protected model when the protected model contains variant parameters with code compile variant activation time. The generated code for the parent model does not contain preprocessor conditional statements for the declarations and definitions of these variant parameters. This code is similar to code generated for such a model when you set the variant parameter activation time to update diagram analyze all choices.

If the parent model uses the same variant parameters as the protected model with code compile activation time, then the generated code for the parent model guards those variant parameters using the preprocessor conditionals #if and #elif.

R2026a: Enable simulation-time tuning of variant parameters in a protected model by specifying associated variant controls as tunable parameters

When you protect a model that uses variant parameters with startup variant activation time by using Protected Model Creator (Simulink Coder), you can make the variant parameters tunable during simulation by specifying only the associated Simulink.VariantControl objects as tunable parameters. Variant parameters with a variant activation time other than startup are not tunable in protected models, so you cannot select their variant controls as tunable parameters. In previous releases, you had to specify the variant parameters also as tunable parameters.

When you protect the model using the Simulink.ModelReference.protect (Simulink Coder) function, specify only the associated Simulink.VariantControl objects by using the TunableParameters (Simulink Coder) name-value argument.

When you get the list of tunable parameters for such a protected model using the Simulink.ProtectedModel.getTunableParameters (Simulink Coder) function, the function returns only the Simulink.VariantControl objects that you specified as tunable parameters.

R2025a: Generate code for variant parameters with code compile activation time defined in a data dictionary linked to a subsystem file

You can generate code for variant parameter objects with variant activation time set to code compile when they are defined in a data dictionary linked to a subsystem file. Previously, code generation was supported for such variant parameters only for variant activation times other than code compile.

R2025a: Define variant parameters in model workspace

You can simulate and generate code for models that define variant parameters in the model workspace. The ActivationTime property of the Simulink.VariantControl object used as the variant control variable for the variant parameter must be set to update diagram, update diagram analyze all choices, or startup. The objects associated with the variant parameter object such as the Simulink.VariantControl object, the Simulink.Parameter object used to set the Specification property, and any Simulink.Parameter objects used as values of the variant parameter must be defined in the model workspace along with the parameter.

For more information, see Configure Variant Parameter Values for Instances of Referenced Models.

R2025a: Configure code generation for variant parameters in model workspace using Code Mappings editor

You can use the Code Mappings editor to configure the code generation attributes for ERT-based and GRT-based targets for Simulink.VariantVariable and Simulink.VariantControl objects defined in the model workspace of a model. The objects are listed in the Code Mappings editor if:

• The Simulink.VariantControl object has its Value property set to a Simulink.Parameter object.

• The Simulink.VariantVariable has its Specification property set to a Simulink.Parameter object.

For more information, see Configure Code Generation for Variant Parameters in Model Workspace Using Code Mappings Editor (Simulink Coder).

R2023a: New Bank property

You can use the Bank property to add a Simulink.VariantVariable object to a variant parameter bank (Simulink.VariantBank).