Share Data Within a Single App Designer App

When you create an app, you can share data between the different components of the app. Using properties is the recommended way to share data across app components because properties are accessible to all functions and callbacks in an app. For example, you can store a value in a property and then update the value using different app components.

If you define an app property, you can access the property value anywhere in your app code using this syntax:

app.Property

Similarly, you can access built-in properties of app UI components using this syntax:

app.Component.Property

For information on sharing data between multiple apps instead, see Share Data Between Multiple App Designer Apps.

Define an App Property

You can choose to define app properties as either private or public depending on how accessible you want the data to be. Use private properties to store data to be shared within the app only. Use public properties to store data to be shared inside and outside of the app (for example, with a script, function, or other app that needs access to the data).

Code View provides a couple ways to create a property:

  • On the Editor tab, expand the drop-down list from the bottom half of the Property button. Select Private Property or Public Property.

    Property button on the App Designer toolstrip, showing the options to add a private property or a public property

  • In the Code Browser, click the Properties tab, expand the drop-down list using the Plus button, and select Private Property or Public Property.

    Properties tab in the Code Browser. The tab contains a search box to find properties and a plus button to add a new property.

After you select an option to create an app property, App Designer adds a property definition and a comment to a properties block in the app code.

properties (Access = private)
    Property % Description
end

The properties block is editable, so you can change the name of the property and edit the comment to describe the property. For example, this private property stores a value for average cost.

properties (Access = private)
    X % Average cost
end

To set a property value when the app starts, you can specify a default value in the properties block or in the startupFcn callback. For example, this property has a value of 5 when the app starts.

properties (Access = private)
    X = 5 % Average cost
end

To restrict the types of values that a property can store, associate a data type with the property in the property definition. For example, this code requires that values assigned to the X property must be of a type that is compatible with double. The X property stores any assigned values as type double.

properties (Access = private)
    X double = 5 % Average cost
end

Access a Property

Once you define an app property, you can access and set the property value anywhere in your app code by using the syntax app.PropertyName. For example, get the current value of the X property and then set its value to 10.

y = app.X  % Get the value of X
app.X = 5; % Set the value of X

Public properties can also be accessed outside the app using the same syntax.

App components also have built-in properties. For example, if your app includes a button component named Button1, you can access the Button object using app.Button1, and you can access the built-in Text property of the button using app.Button1.Text.

Example: Share Plot Data and a Drop-Down List Selection

Open App

You can share data within an app by setting the value of an app property using one component and accessing that property from another component. In this example app, a user can set the sample size of plotted data by using an edit field component and then click a button component to plot data using the new sample size.

The right side of the app displays a plot. The left side of the app shows three components: a Sample Size edit field, a Colormap drop-down list, and an Update Plot button.

To make data accessible to all components, store the data in an app property. In this example, the app stores plot data in a private property named Z.

classdef ConfigurePlotAppExample < matlab.apps.AppBase
    % ...
    properties (Access = private)
        Z = peaks(35); % Surface data to plot
    end
    % ...
end

You can access the value of an app property from any component or function within the app. In this example, the plotsurface function within the app accesses the value of the Z property when plotting data.

function plotsurface(app)
    % Plot Z
    surf(app.UIAxes,app.Z);
    % Set the colormap
    cmap = app.ColormapDropDown.Value;
    colormap(app.UIAxes,cmap);
end

You can update an app property value in response to an app user interacting with the app. In this example, if an app user changes the sample size, the callback function for the edit field updates the value of Z.

function SampleSizeEditFieldValueChanged(app,event)
    sampleSize = app.SampleSizeEditField.Value;
    % Update the Z property
    app.Z = peaks(sampleSize);
end

If the app user pushes the Update Plot button, its callback function updates the plot with the new value of Z by calling the plotsurface function.

Then, you can update the plot with the new value of Z by calling the plotsurface function from the Update Plot button callback.

function UpdatePlotButtonPushed(app,event)
    plotsurface(app);
end

See Also

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