Handle Input Specification Changes

This example shows how to control the input specifications for a System object™. You can control what happens when an input specification changes.

You can also restrict whether the input complexity, data type, or size can change while the object is in use. Whichever aspects you restrict cannot change until after the user calls release.

React to Input Specification Changes

To modify the System object algorithm or properties when the input changes size, data type, or complexity, implement the processInputSpecificationChangeImpl method. Specify actions to take when the input specification changes between calls to the System object.

In this example, processInputSpecificationChangeImpl changes the isComplex property when either input is complex.

properties(Access = private)
    isComplex (1,1) logical = false;
end

methods (Access = protected)
    function processInputSpecificationChangeImpl(obj,input1,input2)
        if(isreal(input1) && isreal(input2))
            obj.isComplex = false;
        else
            obj.isComplex = true;
        end
    end
end

Restrict Input Specification Changes

To specify that the input complexity, data type, and size cannot change while the System object is in use, implement the isInputComplexityMutableImpl, isInputDataTypeMutableImpl, and isInputSizeMutableImpl methods to return false. If you want to restrict only some aspects of the System object input, you can include only one or two of these methods.

methods (Access = protected)
   function flag = isInputComplexityMutableImpl(~,~)
       flag = false;
   end
   function flag = isInputSizeDataTypeImpl(~,~)
       flag = false;
   end
   function flag = isInputSizeMutableImpl(~,~)
       flag = false;
   end
end

 Complete Class Definition File

This Counter System object restricts all three aspects of the input specification.

classdef Counter < matlab.System
    %Counter Count values above a threshold
    
    properties
        Threshold = 1
    end
    
    properties (DiscreteState)
        Count
    end
    
    methods
        function obj = Counter(varargin)
            setProperties(obj,nargin,varargin{:});
        end
    end
    
    methods (Access=protected)
        function resetImpl(obj)
            obj.Count = 0;
        end
        
        function y = stepImpl(obj, u1)
            if (any(u1 >= obj.Threshold))
                obj.Count = obj.Count + 1;
            end
            y = obj.Count;
        end
        
        function flag = isInputComplexityMutableImpl(~,~)
            flag = false;
        end
        
        function flag = isInputDataTypeMutableImpl(~,~)
            flag = false;
        end
        
        function flag = isInputSizeMutableImpl(~,~)
            flag = false;
        end
    end
end