MATLAB Validation Functions

MATLAB^® defines functions for use in property validation. These functions support common use patterns for validation and provide descriptive error messages. The following tables categorize the MATLAB validation functions and describe their use.

Validate Property Using Functions

Use property validation functions in class definitions to impose specific restrictions on property values. A validation function accepts a potential property value as an argument and issues an error if the value does not meet the specific requirement imposed by the function.

During the validation process, MATLAB passes the value to each validation function listed in the class definition. MATLAB calls each function from left to right and throws the first error encountered. The value passed to the validation functions is the result of any conversion applied by the class and size specifications. For more information on class and size validation, see Property Class and Size Validation.

For a list of MATLAB validation functions, see MATLAB Validation Functions.

classdef MyClass
   properties
      Prop {fcn1,fcn2} = defaultValue
   end
end

properties
   Prop {mustBeGreaterThan(Prop,10)}
end

classdef ValidatorFunction
   properties
      Data {mustBeNumeric, mustBeFinite}
      Interp {mustBeMember(Interp,{'linear','cubic','spline'})} = 'linear'
   end
end

a = ValidatorFunction

a = 

  ValidatorFunction with properties:

      Data: []
    Interp: 'linear'

a.Data = 'cubic'

Error setting property 'Data' of class 'ValidatorFunction':
Value must be numeric.

properties
   Data double {mustBeNumeric, mustBeFinite}
end

a.Data = 'cubic'

a = 

  ValidatorFunction with properties:

      Data: [99 117 98 105 99]
    Interp: 'linear'

a = ValidatorFunction;
a.Interp = 'cu'

Error setting property 'Interp' of class 'ValidatorFunction':
Value must be a member of this set
    linear
    cubic
    spline

classdef InterpMethod
   enumeration
      linear
      cubic
      spline
   end
end

classdef ValidatorFunction
   properties
      Data {mustBeNumeric, mustBeFinite}
      Interp InterpMethod
   end
end

a = ValidatorFunction;
a.Interp = 'cu'

a = 

  ValidatorFunction with properties:

      Data: []
    Interp: cubic

Define Validation Functions

Validation functions are ordinary MATLAB functions that are designed for the specific purpose of validating property and function argument values. Functions used to validate properties:

Creating your own validation function is useful when you want to provide specific validation that is not available using the MATLAB validation functions. You can create local functions within the class file or place the function on the MATLAB path to be available for use in any class.

For example, the ImgData class uses a local function to define a validator that restricts the Data property to only uint8 or uint16 values, excluding subclasses and not allowing conversion from other numeric classes. The predefined validation function mustBeInRange restricts the range of allowed values.

classdef ImgData
    properties
        Data {mustBeImData(Data),mustBeInRange(Data,0,255)} = uint8(0)
    end
end
function mustBeImData(a)
    if ~(isa(a,'uint8') || isa(a,'uint16'))
        error("Value of Data property must be uint8 or uint16 data.")
    end
end

When you create an instance of the ImgData class, MATLAB validates that the default value is a uint8 or uint16 value, in the range 0...255, and not empty. Note that the default value must satisfy the validation requirements like any other value assigned to the property.

a = ImgData

a = 

  ImgData with properties:

    Data: 0

Property assignment invokes the validators in left-to-right order. Assigning a char vector to the Data property causes an error thrown by mustBeImData.

a.Data = 'red';

Error setting property 'Data' of class 'ImgData'.
Value of Data property must be uint8 or uint16 data.

Assigning a numeric value that is out of range causes an error thrown by mustBeInRange.

a.Data = uint16(312);

Error setting property 'Data' of class 'ImgData'. Value must be greater
than or equal to 0, and less than or equal to 255.

For related functions, see mustBeInteger, mustBeNumeric, and mustBePositive.