MATLAB CLASSES getter and setters

Question

I come from a Java background. I am having issues with classes in Matlab particularly getters and setters. getting a message saying conflict between handle and value class I'm a little lost with what to do so any help for lack of a better word will be helpful.

classdef Person
properties(Access = private)
    name;
    age; 
end


methods
    % class constructor
    function obj = Person(age,name)         
             obj.age = age;
             obj.name = name;
    end

    %getters
    function name = get.name(obj)          
    end

    function age = get.age(obj)
    end

    %setters
    function value = set.name(obj,name)
    end

    function value = set.age(obj,age)
    end

end

end

Answer 1

Implementation

Since your class is currently a subclass of the default Value class, your setters need to return the modified object:

function obj = set.name(obj,name)
end
function obj = set.age(obj,age)
end

From the documention: "If you pass [a value class] to a function, the function must return the modified object." And in particular: "In value classes, methods ... that modify the object must return a modified object to copy over the existing object variable".

Handle classes (classdef Person < handle) do not need to return the modified object (like returning void):

function [] = set.name(obj,name)
end
function [] = set.age(obj,age)
end

Value vs. Handle

Going a bit deeper, the difference between a Value class and a Handle class lies mostly in assignment:

• Assigning a Value class instance to a variable creates a copy of that class.
• Assigning a Handle class instance to a variable create a reference (alias) to that instance.

The Mathworks has a good rundown on this topic. To paraphrase their illustration, the behavior of a Value class is

% p  is an instance of Polynomial
p = Polynomial(); 
% p2 is also an instance of Polynomial with p's state at assignment
p2 = p;

and of a Handle class is

% db is an instance of Database
db = Database();
% db2 is a reference to the db instance
db2 = db;