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Using Callback Routines

You can define MATLAB expressions that execute when the block diagram or a block is acted upon in a particular way. These expressions, called callback routines, are associated with block or model parameters. For example, the callback associated with a block's OpenFcn parameter is executed when the model user double-clicks on that block's name or path changes.

To define callback routines and associate them with parameters, use the set_param command (see set_param).

For example, this command evaluates the variable testvar when the user double-clicks on the Test block in mymodel:

You can examine the clutch system (clutch.mdl) for routines associated with many model callbacks.

These tables list the parameters for which you can define callback routines, and indicate when those callback routines are executed. Routines that are executed before or after actions take place occur immediately before or after the action.

Table 3-6: Model Callback Parameters 
Parameter
 When Executed
CloseFcn
 Before the block diagram is closed.
PostLoadFcn
 After the model is loaded. Defining a callback routine for this parameter might be useful for generating an interface that requires that the model has already been loaded.
InitFcn
 Called at start of model simulation.
PostSaveFcn
 After the model is saved.
PreLoadFcn
 Before the model is loaded. Defining a callback routine for this parameter might be useful for loading variables used by the model.
PreSaveFcn
 Before the model is saved.
StartFcn
 Before the simulation starts.
StopFcn
 After the simulation stops. Output is written to workspace variables and files before the StopFcn is executed.

Table 3-7: Block Callback Parameters 
Parameter
 When Executed
CloseFcn
 When the block is closed using the close_system command.
CopyFcn
 After a block is copied. The callback is recursive for Subsystem blocks (that is, if you copy a Subsystem block that contains a block for which the CopyFcn parameter is defined, the routine is also executed). The routine is also executed if an add_block command is used to copy the block.
DeleteFcn
 Before a block is deleted. This callback is recursive for Subsystem blocks.
DestroyFcn
 When block has been destroyed.
InitFcn
 Before the block diagram is compiled and before block parameters are evaluated.
LoadFcn
 After the block diagram is loaded. This callback is recursive for Subsystem blocks.
ModelCloseFcn
 Before the block diagram is closed. This callback is recursive for Subsystem blocks.
MoveFcn
 When block is moved or resized.
NameChangeFcn
 After a block's name and/or path changes. When a Subsystem block's path is changed, it recursively calls this function for all blocks it contains after calling its own NameChangeFcn routine.
OpenFcn
 When the block is opened. This parameter is generally used with Subsystem blocks. The routine is executed when you double-click on the block or when an open_system command is called with the block as an argument. The OpenFcn parameter overrides the normal behavior associated with opening a block, which is to display the block's dialog box or to open the subsystem.
ParentCloseFcn
 Before closing a subsystem containing the block or when the block is made part of a new subsystem using the new_system command (see new_system).
PreSaveFcn
 Before the block diagram is saved. This callback is recursive for Subsystem blocks.
PostSaveFcn
 After the block diagram is saved. This callback is recursive for Subsystem blocks.
StartFcn
 After the block diagram is compiled and before the simulation starts.
StopFcn
 At any termination of the simulation.
UndoDeleteFcn
 When a block delete is undone.


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