Automatically update attributes of a class ?

Hi everyone.

I have a class called "Rect" (rectangle) which has 4 attributes: lenght (l), breadth (b), area (A) and perimeter (P). I wish to initialize the class using only the length and breadth and I want it to calculate the area and perimeter automatically. Later when I change its length or breadth I want the class to update the value of its area and perimeter automatically. I have been able to do this in python using the "@property" syntax as I have shown below:

class Rect:
    def __init__(self, _l, _b):
        self.l= _l #lenght
        self.b= _b #breadth
        pass
            
    @property
    def A(self): #area of rectangle
        return self.l*self.b
   
    @property
    def P(self): #perimeter of rectangle
        return 2*(self.l+self.b)

Following is an example of object in python:

rect_1= Rect(2, 3)
print(rect_1.A)
    6
    
rect_1.l= 3
print(rect_1.A)
    9

I wish to do exactly this in MATLAB, is there any equivalent?

Answer 1

[Matt J]

This has to go in a file called Rect.m :

classdef Rect
    
    properties
        l,b
    end
    
    properties (Dependent,Hidden)
        
        A,P
        
    end
    
    methods
        function obj=Rect(l,b)        
            obj.l=l; obj.b=b;
        end
        
        function A=get.A(obj)
          A=obj.l*obj.b;
        end
        function P=get.P(obj)
          P=obj.l+obj.b;
        end            
    end
    
end

and now you would do

>> rect_1= Rect(2, 3); rect_1.A

    
>> rect_1.l= 3; rect_1.A

[Neelay Doshi]

This is exactly what I wanted! Thank you!

[Matt J]

You're welcome, but please Accept-click the answer to indicate so.