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
Specify validation functions as a commaseparated list of function names or function calls with arguments, enclosed in braces.
classdef MyClass properties Prop {fcn1,fcn2,...} = defaultValue end end
MATLAB passes the potential property value to the validation function implicitly. However, if the validation function requires input arguments in addition to the potential property value, then you must include both the property and the additional arguments. Additional arguments must be literal values and cannot reference variables. Literal values are nonsymbolic representations, such as numbers and text.
For example, consider the function mustBeGreaterThan
. It requires a limiting value as an input parameter. This validation function requires that a property value must be greater than this limiting value.
Pass the property as the first argument. Use the property name, but do not enclose the name in quotation marks. This property definition restricts Prop
to values greater than 10
.
properties Prop {mustBeGreaterThan(Prop,10)} end
The following class specifies validation functions for each property.
Data
must be numeric and finite.
Interp
must be one of the three options listed. Specify a default value for this property to satisfy this requirement.
classdef ValidatorFunction properties Data {mustBeNumeric, mustBeFinite} Interp {mustBeMember(Interp,{'linear','cubic','spline'})} = 'linear' end end
Creating a default object of the class shows the initial values.
a = ValidatorFunction
a = ValidatorFunction with properties: Data: [] Interp: 'linear'
Assigning values to properties calls the validation functions.
a.Data = 'cubic'
Error setting property 'Data' of class 'ValidatorFunction':
Value must be numeric.
Because the Data
property validation does not include a numeric class, there is no conversion of the char
vector to a numeric value. If you change the validation of the Data
property to specify the class as double
, MATLAB converts the char
vector to a double
array.
properties Data double {mustBeNumeric, mustBeFinite} end
The assignment to the char
vector does not produce an error because MATLAB converts the char
vector to class double
.
a.Data = 'cubic'
a = ValidatorFunction with properties: Data: [99 117 98 105 99] Interp: 'linear'
Assignment to the Interp
property requires an exact match.
a = ValidatorFunction;
a.Interp = 'cu'
Error setting property 'Interp' of class 'ValidatorFunction':
Value must be a member of this set
linear
cubic
spline
Using an enumeration class provides inexact matching and case insensitivity.
Property validation using an enumeration class provides these advantages:
Inexact, caseinsensitive matching for unambiguous char vectors or string scalars
Conversion of inexact matches to correct values
For example, suppose that you define the InterpMethod
enumeration class for the Interp
property validation.
classdef InterpMethod enumeration linear cubic spline end end
Change the Interp
property validation to use the InterpMethod
class.
classdef ValidatorFunction properties Data {mustBeNumeric, mustBeFinite} Interp InterpMethod end end
Assign a value matching the first few letters of 'cubic'
.
a = ValidatorFunction;
a.Interp = 'cu'
a = ValidatorFunction with properties: Data: [] Interp: cubic
MATLAB defines functions for use in property validation. These functions support common use patterns for property validation and provide descriptive error messages. This table lists the MATLAB validation functions, their meanings, and the MATLAB functions used by the validation functions.
Name  Meaning  Dependencies 

 
 

 

 
 
 
 

 

 
 
 
 
 
 
 

 
 


Validator functions are ordinary MATLAB functions that are designed for the specific purpose of validating property values. Functions used as property validators:
Accept the potential property value as an input argument
Do not return values
Throw errors if the validation fails
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 ImData
class uses a local function to define a validator that restricts the Data
property to a specific range of numeric values.
classdef ImData properties Data {mustBeNumeric, mustBeInRange(Data,[0,255])} = 0 end end function mustBeInRange(a,b) if any(a(:) < b(1))  any(a(:) > b(2)) error(['Value assigned to Data property is not in range ',... num2str(b(1)),'...',num2str(b(2))]) end end
When you create an instance of the ImData
class, MATLAB validates that the default value is numeric, in the range 0...255
, and not empty.
a = ImData
a = ImData with properties: Data: 0
Property assignment invokes the validators in lefttoright order. Assigning a char
vector to the Data
property causes an error thrown by mustBeNumeric
.
a.Data = 'red'
Error setting property 'Data' of class 'ImData':
Value must be numeric.
Assigning a numeric value that is out of range causes an error thrown by mustBeInRange
.
a.Data = 1
Error setting property 'Data' of class 'ImData':
Value assigned to Data property is not in range 0...255
Support MATLAB validation functions for objects of your class by implementing the dependent functions as methods of your class. To determine which methods to implement for each function, see the validation function reference pages listed in this table MATLAB Validation Functions.
For example, suppose that you want your class to support the mustBeGreaterThan
validation function. Overload these MATLAB functions as methods in your class:
isreal
— Always return logical true
because mustBeGreaterThan
does not support complex numbers.
gt
— The second object in the comparison must be scalar, as required by mustBeGreaterThan
.
The SupportmBGT
class implements support for mustBeGreaterThan
.
classdef SupportmBGT properties Prop(1,1) double {mustBeReal} end methods function obj = SupportmBGT(data) if nargin > 0 obj.Prop = data; end end function tf = isreal(obj) tf = true; end function tf = gt(obj1, obj2) tf = [obj1(:).Prop] > obj2.Prop; end end end
Use mustBeGreaterThan
with objects of this class:
a = SupportmBGT(10); b = SupportmBGT(12); mustBeGreaterThan(a,b)
Error using mustBeGreaterThan (line 19)
Value must be greater than the comparison value.