seems like a handle class nesting bug

2 次查看（过去 30 天）
Stuart MacGregor
Stuart MacGregor 2023-5-21
评论： Stuart MacGregor 2023-5-21
classdef IqReader < handle
properties
fid=0
end
...
end
classdef InReader < handle
properties
reader=IqFileReader()
end
...
end
classdef T1Reader < InReader
...
end
classdef T2Reader < InReader
...
end
t1=T1Reader();
t2=T2Reader();
assert(t1.reader ~= t2.reader);
In the example above (when split into files as matlab requires), t1 and t2 get the same handle class object as a reader. e.g. changing t1.reader.fid changes t2.reader.fid
This does not seem right to me.
  2 个评论
Stuart MacGregor
Stuart MacGregor 2023-5-21
cut and paste bug in example: first class should be IqFileReader
Image Analyst
Image Analyst 2023-5-21
Then edit it to correct the first post rather than post the correction as a comment.

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回答（1 个）

Steven Lord
Steven Lord 2023-5-21
Not a bug. See the "Handle Objects as Default Property Values" section on this documentation page for an expanation and an alternate approach to give each instance of the class a separate handle object as its property.
  2 个评论
Stuart MacGregor
Stuart MacGregor 2023-5-21
The doc is unclear re my example however. It says different instances get the same handle-derived property: ok, but my example did not have different instances of the same class, it had two different derived classes, each with a single instance.
This is not good, and not documented. Call it an undocumented feature rather than a bug possibly.
Stuart MacGregor
Stuart MacGregor 2023-5-21
However, it does seem good practice to initialise handle derived properties in the constructor - the behaviour if you don't is very unlikely to be desired, or expected.

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