I wrote the following code:

I wrote the following code:

classdef agent
  properties
     office_neighbours
     family
     state
   endproperties

    methods
       function obj = agent(m,n)
         obj.family = m;
         obj.state = n;
       endfunction

       function n = updateagent(obj,a,b)
          [obj.office_neighbours(1)] = a;
          [obj.office_neighbours(2)] = b;
          n = obj.office_neighbours;
         endfunction

     endmethods
  endclassdef

Then, from the command line, I send the following commands:

>> x = agent(2,3)
  x =
 [object agent]
>> disp(x.family)
  ans=2
>> disp(x.state)
  ans = [] (0X0)

Similarly, when I call

>> updateagent(x,2,3)

I get the answer

ans = 
2 3

But, when I call

>> x.office_neighbours

I get the following

ans = 
[] (0X0)

I dont know what is going on. Please help me out.

Answer 1

[Walter Roberson]

You are not using a handle object. When you update the object inside the class methods, you are updating a temporary copy of the object, not the original object. You would need to output the object and assign the result over top of the original object to update it.

The rules are different for handle objects, which effectively gives you a pointer to the real object, and assigning into that updates the only copy of the object.

[Stephen23]

http://www.mathworks.com/help/matlab/matlab_oop/comparing-handle-and-value-classes.html

[SL: edited to correct hyperlink]

[Diptangshu Sen]

@ Stephen, the link you posted, does not work.

[Diptangshu Sen]

@ Walter, could you elaborate on how I can proceed to do it correctly? I understand that I am barely updating a copy of the object in the method, I need to access the main object using some pointer or something like that. Any help will be appreciated.

[Diptangshu Sen]

So, I defined the class as a handle. All the methods work fine when I call them from the command prompt. But, when I call them from the main function, trouble arises.

Let me explain.

      for m = 1: 10
    for n = 1:2
      Town(m,n)= agent;
      Town(m,n).family = m;
      Town(m,n).state = 0;
     endfor
  endfor

Here, the following error arises: m undefined in main.m

I have tried all types of workarounds like including m in the constructor method itself. But, the same error appears.

[Walter Roberson]

You define

       function obj = agent(m,n)
         obj.family = m;
         obj.state = n;
       endfunction

so the agent method expects m and n to be provided, but you are invoking

      Town(m,n)= agent;

which invokes agent without any parameter.

However, you have a number of syntax errors that would prevent your code from ever getting invoked. You are missing a number of end statements. You also have calls to the undefined functions endfor, endfunction, and endproperties

[Diptangshu Sen]

I changed the constructor method to one without any arguments. Even, the first one called with agent(m,n) threw the same error. I bet the problem is something else. Also, I could not get what you were talking about end statements.

[Walter Roberson]

You are not using MATLAB. You are using Octave, which is a different programming language. We do not have the knowledge or resources to assist with differences between MATLAB and octave. You should consult an octave resource, or else you should rewrite in MATLAB and test in MATLAB.

If you choose to test in MATLAB then we will need to see your revised class definition and calling code.