Validate Property and Input Values

This example shows how to verify that the inputs and property values given to your System object™ are valid.

Validate a Single Property

To validate a property value, independent of other properties, use MATLAB class property validation. This example shows how to specify a logical property, a positive integer property, and a string property that must be one of three values.

 properties
    UseIncrement (1,1) logical = false
    WrapValue (1,1) {mustBePositive, mustBeInteger} = 1
    Color (1,1) string {mustBeMember(Color, ["red","green","blue"])} = "red"
 end

Validate Interdependent Properties

To validate the values of two or more interdependent properties, use the validatePropertiesImpl. This example shows how to write validatePropertiesImpl to verify that a logical property (UseIncrement) is true and the value of WrapValue is larger than Increment.

 methods (Access = protected)
    function validatePropertiesImpl(obj)
        if obj.UseIncrement && obj.WrapValue > obj.Increment
          error("Wrap value must be less than increment value");
        end
    end
 end

Validate Inputs

To validate input values, use the validateInputsImpl method. This example shows how to validate that the first input is a numeric value.

methods (Access = protected)
   function validateInputsImpl(~,x)
      if ~isnumeric(x)
         error("Input must be numeric");
      end
   end
end        

Complete Class Example

This example is a complete System object that shows examples of each type of validation syntax.

classdef AddOne < matlab.System
% ADDONE Compute an output value by incrementing the input value
  
  % All properties occur inside a properties declaration.
  % These properties have public access (the default)
  properties
    UseIncrement (1,1) logical = false
    WrapValue (1,1) {mustBePositive, mustBeInteger} = 10
    Increment (1,1) {mustBePositive, mustBeInteger} = 1
  end

  methods (Access = protected)
    function validatePropertiesImpl(obj)
        if obj.UseIncrement && obj.WrapValue > obj.Increment
          error("Wrap value must be less than increment value");
        end
    end
    
    % Validate the inputs to the object
    function validateInputsImpl(~,x)
        if ~isnumeric(x)
          error("Input must be numeric");
        end
    end
        
    function out = stepImpl(obj,in)
      if obj.UseIncrement
        out = in + obj.Increment;
      else
        out = in + 1;
      end
    end    
  end
end