[Octave-bug-tracker] [bug #52614] setting properties of classdef object during construction with inheritance

[Amro]

URL:
  <http://savannah.gnu.org/bugs/?52614>

                 Summary: setting properties of classdef object during
construction with inheritance
                 Project: GNU Octave
            Submitted by: amro_octave
            Submitted on: Thu 07 Dec 2017 05:56:19 PM EET
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.1
        Operating System: Any

    _______________________________________________________

Details:

I have a simple class hierarchy with two classes:

* In the base class, the constructor calls a method which initializes some
properties.

* In the derived class, I override said method (while still calling the parent
method). The constructor also invokes the parent constructor.

Here is a minimal example:

$ cat ClassA.m


classdef ClassA < handle
    properties
        a
    end

    methods
        function obj = ClassA()
            disp('-- ClassA.ClassA')
            obj.foo();
        end

        function foo(obj)
            disp('-- ClassA.foo')
            obj.a = 1;
        end
    end
end


$ cat ClassB.m


classdef ClassB < ClassA
    properties
        b
    end

    methods
        function obj = ClassB()
            disp('-- ClassB.ClassB')
            obj = address@hidden();
        end

        function foo(obj)
            disp('-- ClassB.foo')
            address@hidden(obj);
            obj.b = 2;
        end
    end
end


This works fine in MATLAB (I'm using R2017a):


>> obj = ClassA()
-- ClassA.ClassA
-- ClassA.foo
obj = 
  ClassA with properties:
    a: 1

>> obj = ClassB()
-- ClassB.ClassB
-- ClassA.ClassA
-- ClassB.foo
-- ClassA.foo
obj = 
  ClassB with properties:
    b: 2
    a: 1


But it fails in Octave 4.2.1:


>> obj = ClassA()
-- ClassA.ClassA
-- ClassA.foo
obj = 
<object ClassA>

>> obj = ClassB()
-- ClassB.ClassB
-- ClassA.ClassA
-- ClassB.foo
-- ClassA.foo
error: cannot reference properties of class `ClassB' for non-constructed
object
error: called from
    foo at line 15 column 19
    ClassA at line 9 column 13
    ClassB at line 9 column 17


I did try to incorporate the functionality of the foo method into the
constructor (i.e directly set the properties a and b from the respective
constructors), and the code does work then (both MATLAB and Octave):

$ cat ClassAA.m ClassBB.m


classdef ClassAA < handle
    properties
        a
    end

    methods
        function obj = ClassAA()
            disp('-- ClassAA')
            obj.a = 1;
        end
    end
end

classdef ClassBB < ClassAA
    properties
        b
    end

    methods
        function obj = ClassBB()
            disp('-- ClassBB')
            obj = address@hidden();
            obj.b = 2;
        end
    end
end


Still, I wanted to report this case... Thanks.





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