How to initialize an object array as a class property?

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Sigurd Askeland
Sigurd Askeland 2018-4-20
评论： Steven Lord 2022-7-21
Here are two code snippets illustrating my problem:
classdef SomeClass
properties
foo;
bar;
end
end
and in another file:
classdef SomeOtherClass
properties
%Array of SomeClass objects.
someClassArray;
end
methods
function obj = SomeOtherClass(n)
%Initialize the array, as n can be large.
obj.someClassArray(n,1) = SomeClass();
end
end
end
When initializing an object of the second class, Matlab assusmes the someClassArray property is a double, and gives an error:
The following error occurred converting from SomeClass to double:
Conversion to double from SomeClass is not possible.
Error in SomeOtherClass (line 10)
obj.someClassArray(n,1) = SomeClass();
How do I get around this?

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采纳的回答

Matt J
Matt J 2018-4-20
编辑：Matt J 2018-4-20 
      methods
         function obj = SomeOtherClass(n)
               tmp(n,1)=someClass;
              obj.someClassArray=tmp;
          end
      end
  2 个评论
Jon
Jon 2022-7-21
I have been experiencing the same problem, and this approach also solves my problem. I am wondering though why it is necessary, or why it works when simply initializing the property value directly i.e
obj.someClassArray(n,1) = SomeClass();
doesn't work.
Steven Lord
Steven Lord 2022-7-21
It's because of how property default values are determined. See the "Property Default Values" section on this documentation page for more information.
I'd probably solve this by making someClassArray either a scalar SomeClass object or an empty SomeClass object array (like Prop4 in the documentation section I referenced above.)
But be careful with this if you initialize a property value to an instance of a handle class. See the "Initializing Properties to Handle Objects" section on that same documentation page.

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