Model Callbacks

Model callbacks execute at specified action points, for example after you load or save the model.

You can set most of the same callbacks for libraries. Only the callbacks that can execute for a library are available to set for a library. For example, you cannot set the InitFcn callback for a library, which is called as part of simulation, because you cannot simulate a library.

Create Model Callbacks

In the Simulink^® Editor, open the Property Inspector. In the Modeling tab, under Design, click Property Inspector.
With no selection at the top level of your model, in the Properties tab, in the Callbacks section, select the callback you want to set.
In the box, enter the functions you want the callback to perform.

To create a model callback programmatically, use the set_param function to assign MATLAB^® code to a model callback parameter. See Model Callback Parameters

Referenced Model Callbacks

In a model hierarchy, the execution of callbacks reflects the order in which the top model and the models it references execute their callbacks. For example, suppose:

Model A:
- References model B in accelerator mode.
- Has a PostLoadFcn callback that creates variables in the MATLAB workspace.
- Has the Rebuild configuration parameter set to Always, If changes detected, or If any changes in known dependencies detected.
Model B:
- Has a CloseFcn callback that clears the MATLAB workspace.
- Has not been built or is out of date.

Simulating model A triggers rebuilding the referenced model B. When Simulink rebuilds model B, it opens and closes model B, which invokes the model B CloseFcn callback. CloseFcn clears the MATLAB workspace, including the variables created by the model A OpenFcn callback.

Instead of using a CloseFcn callback for model B, you can use a StopFcn callback in model A to clear the variables used by the model from the MATLAB workspace. Alternatively, you can use a data dictionary for the data to avoid the need to have variables in the base workspace.

If a model references multiple instances of the same model in normal mode, callbacks execute for each instance.

For models referenced in accelerator mode, Simulink does not execute some callbacks. If everything is up to date and the Rebuild configuration parameter is set to If any changes in known dependencies detected, then the referenced model does not compile and its InitFcn callbacks do not execute. Callbacks such as StartFcn and StopFcn do not execute because referenced models in accelerator mode use an S-function, which starts and stops instead of the referenced model.

Note

Simulation outputs are not available in the StopFcn callbacks for command-line simulations.

Model Callback Parameters

Model Loading and Closing Callback Parameters

Model Callback Parameter When Executed

Model Callback Parameter	When Executed
`PreLoadFcn`	This callback is executed before the model is loaded. Do not use model parameters in a `PreLoadFcn` model callback because parameters are loaded after the model is loaded. Instead, use a `PostLoadFcn` callback to work with model parameters when the model is loaded. Defining a callback code for this parameter is useful for loading variables that the model uses. If you want to call your model from a MATLAB file without opening your model, use the `load_system` function so that the `PreLoadFcn` executes. For examples, see: Load Variables When Opening a Model Introduction to Managing Data with Model Reference Manage Simulation Targets for Referenced Models Limitations include: For the `PreLoadFcn` callback, `get_param` does not return the model parameter values because the model is not yet loaded. Instead, `get_param` returns: The default value for a standard model parameter such as `solver` An error message for a model parameter added with `add_param` Programmatic access to Scopes is not supported.
`PostLoadFcn`	After the model is loaded. Defining callback code for this parameter may be useful for generating an interface requiring a loaded model. Limitations include: If you make structural changes with `PostLoadFcn`, the function does not set the model `Dirty` flag to indicate unsaved changes. When you close the model, Simulink does not prompt you to save. Programmatic access to Scopes is not supported. Because the Simulink Editor opens after this callback executes, the `PostLoadFcn` callback is not suitable for setting up the model view, for example setting a zoom factor. Save zoom information with the model to open it with a particular zoom factor.
`CloseFcn`	Before the block diagram is closed. Any `ModelCloseFcn` and `DeleteFcn` callbacks set on blocks in the model are called prior to the model `CloseFcn` callback. The `DestroyFcn` callback of any blocks in the model is called after the model `CloseFcn` callback.

PreLoadFcn

This callback is executed before the model is loaded.

Do not use model parameters in a PreLoadFcn model callback because parameters are loaded after the model is loaded. Instead, use a PostLoadFcn callback to work with model parameters when the model is loaded.

Defining a callback code for this parameter is useful for loading variables that the model uses.

If you want to call your model from a MATLAB file without opening your model, use the load_system function so that the PreLoadFcn executes.

For examples, see:

Limitations include:

For the PreLoadFcn callback, get_param does not return the model parameter values because the model is not yet loaded. Instead, get_param returns:
- The default value for a standard model parameter such as solver
- An error message for a model parameter added with add_param
Programmatic access to Scopes is not supported.

PostLoadFcn

After the model is loaded.

Defining callback code for this parameter may be useful for generating an interface requiring a loaded model.

Limitations include:

If you make structural changes with PostLoadFcn, the function does not set the model Dirty flag to indicate unsaved changes. When you close the model, Simulink does not prompt you to save.
Programmatic access to Scopes is not supported.

Because the Simulink Editor opens after this callback executes, the PostLoadFcn callback is not suitable for setting up the model view, for example setting a zoom factor. Save zoom information with the model to open it with a particular zoom factor.

CloseFcn

Before the block diagram is closed.

Any ModelCloseFcn and DeleteFcn callbacks set on blocks in the model are called prior to the model CloseFcn callback. The DestroyFcn callback of any blocks in the model is called after the model CloseFcn callback.

Model Saving Callback Parameters

Model Callback Parameter	When Executed
`PreSaveFcn`	Before the model is saved.
`PostSaveFcn`	After the model is saved. Note If you make structural changes with `PostSaveFcn`, the function does not set the model `Dirty` flag to indicate unsaved changes. When you close the model, Simulink does not prompt you to save.

Model Simulation Callback Parameters

Model Callback Parameter	When Executed
`InitFcn`	Called during update phase before block parameters are evaluated. This is called during model update and simulation. For more information on `InitFcn` callback, see Initialization Function For examples, see: Create Programmatic Hyperlinks Track Object Using MATLAB Code
`StartFcn`	Called before the simulation phase. This is not called during model update.
`PauseFcn`	After the simulation pauses.
`ContinueFcn`	Before the simulation continues.
`StopFcn`	After the simulation stops. Output is written to workspace variables and files before the `StopFcn` is executed. Simulation outputs are not available in the `StopFcn` callbacks for command-line simulations.

Documentation

Model Callbacks

Create Model Callbacks

Referenced Model Callbacks

Model Callback Parameters

Related Topics

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