Expected one output from a curly brace or dot indexing expression, but there were 2 results, when re-initialize an object array

I am encountering this issue when I was working on clearing/re-initializing an object array.

A sample code snippet is here:

classdef classObj1
    properties
        a;
        b;
        c;
    end
end
classdef classObj2
    properties (Access = private)
        obj1_arr;
    end
    methods
        function addtoArr(obj, e)
            obj.obj1_arr(end + 1) = e;
        end
        
        function clearArr(obj)
            obj.obj1_arr = classObj1.empty(1, 0);
        end
        
        function setArr(obj, r)
            obj.obj1_arr = r;
        end
    end
end

Everytime I create an classObj2, I will initialize its property, so the obj1_arr should be an 1d empty array of classObj1.

a = classObj2();
a.setArr(classObj1.empty(1, 0));

and add something to the array, everything is fine until here.

for i = 1:10
    o = classObj1();
    o.a = 1; o.b = 2; o.c = 3;
    a.addtoArr(o)
end

However, when I try to call the clearArr() function, I get the following error message:

Expected one output from a curly brace or dot indexing expression, but there were 2 results.

on the line:

obj.obj1_arr = classObj1.empty(1, 0);

I have done my work on reading some posts for the reason and solution. e.g. using delete(), clear(), or obj.obj1_arr(:) = []; Unfortunately they don't work, and the identical error message is presented on the same line.

What I am trying to do is just clearing all elements in the obj1_arr since I would like to reuse it later without the data set in previous rounds, which is similar to list.clear() in python.

I appreciate any help that can assist me in solving this issue.

Answer 1

[Shubham Rawat]

Hi Cheng-Hung,

You had done spelling mistake inside the clearArr() function in the following line:

obj.obj1_arr = classObj1.empty(1, 0);

you had written classobj instead it is classObj.

Hope this Helps!

[Cheng-Hung He]

Hi Shubham,

Thanks for your answer! I have modifed the typo. Moreover, I found that the reason this error presented by Matlab is because the way I call the function.

Originally, I call it with

classObj2_arr.clearArr();

where the classObj2_arr is an array of classObj2, and this way incurs this error.

Instead, I should call it with a for loop:

for i = 1:lenth(classObj2_arr)
    classObj2_arr(i).clearArr();
end

Though I have no idea why the first approach cannot be used, this change solves the bug.:)