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Fixed- or variable-size output ports


[flag_1,flag_2,...flag_n] = isOutputFixedSizeImpl(obj)


[flag_1,flag_2,...flag_n] = isOutputFixedSizeImpl(obj) returns whether each output port is fixed size. The number of outputs must match the value returned from the getNumOutputs method, which is the number of output arguments listed in the stepImpl method.

For System objects with one input and one output and where you want the input and output fixed sizes to be the same, you do not need to implement this method. In this case isOutputFixedSizeImpl assumes the input and output fixed sizes are the same and returns the fixed size of the input.

If your System object has more than one input or output or you need the output and input fixed sizes to be different, you must implement the isOutputFixedSizeImpl method to define the output fixed size. You also must use the propagatedInputFixedSize method if the output fixed size status differs from the input fixed size status.

Run-Time Details

During Simulink® model compilation and propagation, the MATLAB System block calls the isOutputFixedSize method, which then calls the isOutputFixedSizeImpl method to determine the output fixed size.

All inputs default to variable-size inputs For these inputs, the output size is the maximum input size.

Method Authoring Tips

  • You must set Access = protected for this method.

  • You cannot modify any properties in this method.

Input Arguments

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System object handle used to access properties, states, and methods specific to the object. If your isOutputFixedSizeImpl method does not use the object, you can replace this input with ~.

Output Arguments

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Logical, scalar value indicating whether the specific output port is fixed size (true) or variable size (false).


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Specify in your class definition file that the output from a System object is of fixed size.

methods (Access = protected)
   function c1 = isOutputFixedSizeImpl(obj)
      c1 = true;

Version History

Introduced in R2013b