Is there any way to set function (or method) output as comma separated list?

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Hyeokjin Jho
Hyeokjin Jho 2018-10-24
评论： Matt J 2022-1-12
If we have an array of struct, like this:
s(1).a = 1;
s(2).a = 2;
s(3).a = 3;
and then if we get the field of this array, then the result would be like:
s.a
ans =
1
ans =
2
ans =
3
As I know, this output is comma separated list.
I want to have this behavior in my method output too, so that I can use my object just as how I use structs. Something like this:
classdef myObject
properties
myProp
end
methods
function this = myObject(input)
%constructor
this.myProp = input;
end
function output = myMethod(this)
% this function should return myProp as comma separated list
% when myObj array 'this' is given
% I don't know what to do here
% My best try:
% anyway the code below here obviously doesn't work...
output = {this(:).myProp}
end
end
and
myObj(1) = myObject('A');
myObj(2) = myObject('B');
myObj(3) = myObject('C');
myObj.myMethod
ans =
A
ans =
B
ans =
C
It would be cool, isn't it?
I tried varargout, but it only outputs explicit number of nargout, so if the output argument is not specified, it will give only one output, which is varargout{1}.
Is there any good way to do this?
  2 个评论
Hyeokjin Jho
Hyeokjin Jho 2018-10-24
So the best way here is something like this? :
someStruct = myObj.myMethod;
someStruct.output
ans =
A
ans =
B
ans =
C
and there is no direct way to output a comma separated list?

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采纳的回答

Matt J
Matt J 2018-10-24
编辑：Matt J 2018-10-24
You should be able to do it by overloading numArgumentsFromSubscript. In other words, tell the class to interpret
>> myObj.myMethod(arg)
as a dot-indexing expression rather than a function call.
The hassle with this is that, similar to overloading subsref, you now have to explicitly implement code in the method to distinguish which dot-indexing expressions are function calls and which are actual indexings.

更多回答（1 个）

Hyeokjin Jho
Hyeokjin Jho 2022-1-12
I found a workaround by using properties with custom get method.
classdef myObject
properties
myProp
end
properties (Dependent,SetAccess = private)
myDepProp
end
methods
function this = myObject(input)
%constructor
this.myProp = input;
end
end
methods
function output = get.myDepProp(this)
output = this.myProp; % operates as singleton
end
end
end
Test:
myObj(1) = myObject('A');
myObj(2) = myObject('B');
myObj(3) = myObject('C');
myObj.myDepProp
ans =
'A'
ans =
'B'
ans =
'C'
  2 个评论
Matt J
Matt J 2022-1-12
编辑：Matt J 2022-1-12
Yes, although I think the example would be clearer if MyDepProp performs some additional work that a class method might, e.g.,
methods
function output = get.myDepProp(this)
output = lower(this.myProp); % operates as singleton
end
end
>>myObj(1) = myObject('A');
>>myObj(2) = myObject('B');
>>myObj(3) = myObject('C');
>> myObj.myDepProp
ans =
'a'
ans =
'b'
ans =
'c'
Matt J
Matt J 2022-1-12
A limitation of this approach, of course, is that it does not allow the "method" to take additional input arguments.

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