Property Definition Block

The properties and end keywords define one or more class properties that have the same attribute settings. This is the general syntax for defining a property block:

properties (attributes)
   propName1
   ...
   propNameN
end

For example, this properties block defines two properties with the SetAccess attribute set to private. This attribute setting means that the property values can be set only by members of the PrivateProps class.

classdef PrivateProps
   properties (SetAccess = private)
      Property1
      Property2
   end
end

You can also define multiple property blocks for properties with different attributes. In this example, one properties block defines properties with private SetAccess, and the second block defines an abstract property. Property blocks with different attributes can appear in any order in the class definition.

classdef MultiplePropBlocks
   properties (SetAccess = private)
      Property1
      Property2
   end
   properties (Abstract)
      Property3
   end
end

For a full listing of property attributes, see Property Attributes.

Property Validation Syntax

Within a properties block, you can use property validation. Property validation enables you to place one or more restrictions on each property value, including size and class. You can also define a default value for each property. The general syntax for property validation is:

properties (attributes)
   propName1 (dimensions) class {validators} = defaultValue
   ...
end

This class defines one property. The properties block has no explicit attribute defined, which is equivalent to defining a block of public properties. MyPublicData must also be a vector of positive doubles, and it has a default value of [1 1 1].

classdef ValidationExample
   properties
      MyPublicData (1,:) double {mustBePositive} = [1 1 1]
   end  
end

Not all validation options must be used at once, and different properties in the same block can use different combinations of validators. In this example, the RestrictedByClass property uses class validation only, while RestrictedByFunction uses a validation function and assigns a default value.

classdef DifferentValidation
   properties
      RestrictedByClass uint32
      RestrictedByFunction {mustBeInteger} = 0
   end
end

For more information, see Property Class and Size Validation and Property Validation Functions.

Property Access Syntax

Property access syntax is like MATLAB structure field syntax. For example, if obj is an object of a class, then you can get the value of a property by referencing the property name.

val = obj.PropertyName

Assign values to properties by putting the property reference on the left side of the equal sign.

obj.PropertyName = val

For example, instantiate the ValidationExample class and read the value of MyPublicData.

classdef ValidationExample
   properties
      MyPublicData (1,:) double {mustBePositive} = [1 1 1]
   end  
end

x = ValidationExample;
x.MyPublicData

ans =

     1     1     1

Assign a new value to the property that satisfies the validators defined for it.

x.MyPublicData = [2 3 5 7];

You can optionally define get and set methods that MATLAB automatically calls when you use this structure field syntax. For more information, see Property Get and Set Methods.

object.(PropertyNameVar)

PropName = "KeyType";
function o = getPropValue(obj,PropName)
   o = obj.(PropName);
end