The Settings window of many types of form objects has a section that allows you to select a node in a tree structure that includes the model tree, or parts of the model tree, and parts of the application tree. Examples include the Source section of an input field or the Choose Commands to Run section of a button. There are many properties in the model and application trees that are not made available by default, because there may be hundreds or even thousands of properties, and the full list would be unwieldy. However, these “hidden” properties may be made available to your application by a technique called Data Access.

The remainder of this section gives an introduction to using Data Access, with examples for input fields and buttons.

By default, you can link input fields to parameters and variables defined in the model tree under the Parameters or Variables nodes and to variables declared in the application tree under the Declarations node. To access additional model tree node properties, click the Switch to Model Builder and Activate Data Access button in the header of the Source section of the input field Settings window, as shown in the figure below.

You can also access it from the Application group of the Developer tab in the Model Builder workspace

or from the Home tab in the Application Builder workspace.

Then, when you click on a model tree node, checkboxes appear next to the individual settings. In the figure below, the checkbox for an Electric potential boundary condition is selected:

The figure below shows the Settings window for an input field. The list of possible sources for this field now contains the Electric potential.

In addition, as shown in the figure above, Data Access allows you to access the Editable checkbox and the Tooltip text of the input field form object. This follows a general pattern: Beyond the settings in the Model Builder, Data Access provides access to certain properties within the Application Builder.

Data Access can be used for buttons to set the value of a parameter, variable, or a model property. For example, you can create buttons for predefined mesh element sizes. The settings shown in the figure below are available when, in the Settings window of the Mesh node, the Sequence type is set to User-controlled mesh. In this example, the Predefined property for Element Size has been made available and then selected.

The figure below shows the Settings window for a button used to create a mesh with Element Size > Predefined set to Fine.

In the above example, a Set Value command is used to set the value of the Predefined mesh size (hauto) property. The property Predefined mesh size (hauto) corresponds to the following settings in the Size node shown earlier:

The value of the hauto property is a double and can take any non-negative value. For non-integer values, linear interpolation is used for the custom mesh parameters. You can, for example, let a slider object adjust the predefined mesh size. For more information on the slider object, see Slider.

In general, for individual model tree properties, you can quickly learn about their allowed values by recording code while changing their values and then reviewing the automatically generated code. For more information, see Recording Code.

You can also use a combo box object to give direct access to all of the options from Extremely fine through Extremely coarse. For more information, see Combo Box.

The table below summarizes the availability of Data Access for form objects and events, as well as menu, toolbar, and ribbon items.

A global event, menu, ribbon, or toolbar item provides a Choose Commands to Run section in its Settings window, to which the functionality described above in the section on buttons also applies. Global events and many form objects provide a Source section in its Settings window, and the functionality described above in the section on input fields applies. For information on global events, menus, ribbons, and toolbar items, see Graphics Toolbar, The Main Window Editor, Events, Table, and Toolbar and Form Toolbar.