How to pass a string into a Matlab function block?

Hello all, I want to pass a string into a Matlab function block.

This string is a mask parameter that must not be evaluated (it's a name). I'll try to pass it via a structure like this:

function Out = GetDiagAvail_mf(structArg)
%#codegen

coder.extrinsic('disp');

Out = coder.nullcopy(uint8(0));

disp(['in EML code, varName = ',structArg.varName]);

Out = coder.ceval('MyFct',coder.opaque('const char *',structArg.varName));

structArg is built in mask Initialization Pane like this: structArg.varName = Param;

'Param' value could be: 'MyString'.

I want to have in generated code: MyFct(MyString);

But I have this error:

_Error c2_lib_DSM.c: 161  undeclared identifier `MyString'
Warning c2_lib_DSM.c: 161   possible usage of MyString before definition 
Warning c2_lib_DSM.c: 318  static `void function(pointer to void,pointer to const incomplete struct mxArray_tag defined at C:\Program Files\MATLAB\R2011b\extern\include\matrix.h 299,pointer to const char,pointer to void) c2_c_sf_marshallIn' is not referenced 
Warning c2_lib_DSM.c: 291  static `pointer to const incomplete struct mxArray_tag defined at C:\Program Files\MATLAB\R2011b\extern\include\matrix.h 299 function(pointer to void,pointer to void) c2_c_sf_marshallOut' is not referenced _
1 errors, 3 warnings

Please, can you help me?

I'm using Matlab 2011b.

Thanks in advance,

Ursula

Answer 1

[Ryan Livingston]

Hi Ursula,

You should simply be able to pass a MATLAB string to coder.ceval:

 Out = coder.ceval('MyFct', structArg.varName);

Note that it will not be null-terminated automatically so that is required if "MyFct" expects a null-terminated C string:

 Out = coder.ceval('MyFct', [structArg.varName char(0)]);

[Maharshi Patel]

Also, to pass a string as an argument to MATLAB function, you will need to uncheck the Tunable option for 'structArg' in the Ports and Data Manager (via 'Edit Data' button in Editor tab)