[Octave-bug-tracker] [bug #56953] Can not access private class properties from lambdas

[Markus Ebner]

URL:
  <https://savannah.gnu.org/bugs/?56953>

                 Summary: Can not access private class properties from lambdas
                 Project: GNU Octave
            Submitted by: seijikun
            Submitted on: Wed 25 Sep 2019 10:55:38 PM UTC
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 5.1.0
        Operating System: Any

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Details:

In Octave, it is not possible to access private class properties (via
self.<propertyname>) from within lambdas defined somewhere in the class.

Here is a small example that works in Matlab:

classdef TestClass
        properties(Access = private)
                privateProperty = 0;
        end
        
        methods
                function self = TestClass()
                        self.privateProperty = 5;
                        fnPtr = @() disp(self.privateProperty);
                        fnPtr();
                end
        end
end


In Octave, this outputs the error:

error: subsref: property `privateProperty' has private access and cannot be
obtained in this context
error: called from
    TestClass>@<anonymous> at line 9 column 16
    TestClass at line 10 column 4


Workaround is one of:
- Remove the Access-clause on the properties
- Set Access to public (protected does not work either)
- Copy variable into "stack" before using it in the lambda, like:

tmpCopy = self.privateProperty;
fnPtr = @() disp(tmpCopy);
fnPtr();
 




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