Unexpected initial property value with Matlab oop

Question

I have defined a simple class called MySettings, which internally holds for others settings defined in a class called MySubSettings:

%% --- Definition for MySubSettings
classdef MySubSettings < handle    
    properties
        Fifi = 666;        
    end    
end

%% --- Definition for MySettings
classdef MySettings < handle    
    properties
        Riri = 42; 
        Subs = MySubSettings();
    end   
end

The first time I instantiate MySettings with s = MySettings(); everything is ok (Property Riri is initialized to 42 and Subs is an instance of MySubSettings with property Fifi initialized to 666) ... So far so good ...

Now if I modify property values and reassign s to new instance like this:

s.Riri = 0;
s.Subs.Fifi = 0;
s = MySettings();

Then inspecting new values for properties in new s instance ... I have s.Riri which is equal to 42 (as expected) ... but s.Subs.Fifi is still equal to 0 where I would have expected it to be reinitialized to 666 (???)

Why only Riri is initialized ? Am I doing something wrong or is it a bug ?

Note: I have the issue with R2013b and R2014b.

welcome to the wonderful world of MATLAB OOP :)

gregswiss
– gregswiss

2015-10-23 10:44:59 +00:00
Commented Oct 23, 2015 at 10:44 — gregswiss
– gregswiss, Commented Oct 23, 2015 at 10:44

CitizenInsane · Accepted Answer · 2015-04-23 10:44:09Z

3

My misunderstanding ...

Values assigned to properties in class definition are not initial values (like in C# for instance) BUT default values and are no longer re-evaluated after the class is first used.

In my example, as MySubSettings is a handle class, any value assigned to it becomes the new default for next instances.

This default value concept is a bit confusing ... but ok, it was my mistake ... sorry.

answered Apr 23, 2015 at 10:44

CitizenInsane

4,8852 gold badges29 silver badges63 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Sam Roberts Over a year ago

This is correct. To get the behaviour you were expecting, assign the initial value for MySubSettings within the constructor of mySettings, rather than as a default property value. For a criticism of this design of MATLAB OO, see @Yair 's recent article on his UndocumentedMATLAB blog, and for a defence of it see the comments to the article from me and Dave Foti.

CitizenInsane Over a year ago

@SamRoberts Thanks for these clarifications, I was indeed wondering why to have such 'default value' concept and not just simply 'per instance initialization'.

Collectives™ on Stack Overflow

Unexpected initial property value with Matlab oop

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related