Unable to clear classes

조회 수: 85(최근 30일)
Jim Hokanson
Jim Hokanson 2012년 10월 23일
답변: Fuad Numan 2016년 2월 4일
At times I am unable to clear classes in Matlab without restarting the program. This seems to be related to errors being thrown in the class. In other words, following an error I might make a change to the class and then call "clear classes" to reset everything. Also, since 95% of the time I am working with handle classes, this may be handle class related.
Some issues I have run across that I know are not currently the problem are: 1) storage of the class in a figure which is still open 2) the default value of a property being a class
Thanks, Jim
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Jim Hokanson
Jim Hokanson 2012년 11월 27일
I have confirmed with TMW that the example I provided below is a bug. Unfortunately I have not yet received a bug ID. One of the problems I identified (there may be more) is when children hold onto a reference of the parent object, and the parent holds onto a reference of the children. This only occurs when there are more than 2 children.
A workaround:
N = 4 %number of children
for iChild = 1:N
tempChildren(iChild) = child_class(parent_class);
parent_class.children = tempChildren;
%NOTE: In the child we have something like
function obj = child_class(parent_obj)
obj.parent = parent_obj;
The bug would occur in this case below: These are both handles clases
parent_class.children = child_class(parent_class,4)
function obj = child_class(parent_obj,N)
if nargin == 0
obj(N) = child_class;
for iObj = 1:N
obj(iObj) = child_class;
obj.parent = parent_obj;

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채택된 답변

Jim Hokanson
Jim Hokanson 2013년 4월 27일
This is a bug:
It has been fixed in 2013a

추가 답변(7개)

Sean de Wolski
Sean de Wolski 2012년 10월 24일
Hi Jim,
Are you saving the objects to or loading from a *.mat file? If so please see:
This bug report doesn't highlight the workaround though, which is to not store the *.mat files with -v7.3 formatting.
  댓글 수: 7
Matt J
Matt J 2012년 11월 7일
Never mind, I was able to reproduce the problem with
clear classes;
This was even without the directory structure you specified, and it was in R2012a. Also, "clear classes" always gives me a warning.

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Malcolm Lidierth
Malcolm Lidierth 2012년 11월 7일
Object references can leak via userdata or appdata, callbacks, the variable editor etc. Try closing all figures - but probably close the variable editor first.
With handle classes I have taken to maintaing a list in the figure appdata area maintained by calling a common superclass method from the constructors, and adding a DeleteFcn callback that calls a static superclass method to delete any remaining valid handle objects when a figure closes. A bit of a pain but it seems to work.

Matt J
Matt J 2012년 10월 24일
Just a thought. Try doing REHASH. Then clear classes again.
  댓글 수: 2
Matt J
Matt J 2012년 10월 24일
what about my latest comments/questions above?

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Daniel Shub
Daniel Shub 2012년 10월 25일
Two related, but not duplicate, questions are
There was also a related question sometime in the past few months where it eventually seemed like the problem was a bug (the problem disappeared in some release) It involved two classes calling each other. I can no longer find the question (which isn't surprising give the search capabilities of Answers).

Matt J
Matt J 2012년 11월 7일
편집: Matt J 2012년 11월 8일
Based on your example with class_1 and class_2, I think the problem is related to the fact that you are creating handle objects which contain shared copies of themselves (the temp property is passed copies of obj itself in the constructor). I can't explain why the problem occurs only for N>2, however, it's easy to see that you create a chicken-and-egg situation when MATLAB tries to delete an object of class_1: before MATLAB can delete an object of class_1, it must first delete all the data in the properties that it contains. However, the properties of the class_1 object contain the object itself!
Is there any way you can settle for unshared copies of class_1 in temp?
  댓글 수: 5
Malcolm Lidierth
Malcolm Lidierth 2012년 11월 9일
Does subclassing hgsetget instead of handle help? Standard handle graphics always have a parent/child hierarchy.
Do the classes need to be in the same package?
I do not recall recognizing this behaviour in my own classes (but all use hgsetget and never use packages - in MATLAB anyway).
However, I do have isvalid tests in the delete methods on the instance being deleted because function delete(obj) sometimes gets a valid and sometimes an invalid obj. I think this problem may (??) be related - at what stage during deletion does isvalid return false when there are leaks, and what order does MATLAB delete a circular reference. obj.delete() can get called even when obj.isvalid() returns false. Is it the MATLAB delete equivalent of referencing "this" in a constructor in e.g. Java.

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Chris Wiak
Chris Wiak 2016년 2월 4일
I have the same problem in Matlab 2015b. 'clear classes' throws a warning. Any thoughts on this one?

Fuad Numan
Fuad Numan 2016년 2월 4일
This will clear a specific variable (Class1) from the main Class (ClassStore).

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