When subclassing "double" with new properties, is there an easy way to access the data value?

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Robbie
Robbie 2022-7-11
编辑： Aaron Kaw 2023-11-6
Say I have a class subclassing double, and I want to add a string (Similar to the 'extendDouble' in the documentation). Is there an easy way to access the actual numeric value without the extra properties, particular for reassigning? Or if I want to change the value, will I have to recreate the value as a new member of the class with the new value and the same string?
e.g.
classdef myDouble < double
properties
string
end
methods
function obj = myDouble(s)
% Construct object (simplified)
obj.string = s;
end
end
end
----------
x = myDouble(2,'string')
x =
2 string
x = 3
x =
3 string

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采纳的回答

Jeffrey Clark
Jeffrey Clark 2022-7-13
编辑：Jeffrey Clark 2022-7-13
@Robbie, see Subclasses of Built-In Types with Properties - MATLAB & Simulink (mathworks.com)
Sorry but the subsasgn and subsref will be needed (and maybe numArgumentsFromSubscript) just follow the example given, or use Customize Object Indexing - MATLAB & Simulink (mathworks.com) for MATLAB 2021b+ preferred pattern (but it isn't any easier or closer to what you really want).
It would be easier to not subclass a basic type, just have two properties for the string and numeric. Then when referencing the obj.property you get all the appropriate property functions like sqrt(x.val) and disp(['string is ' x.str]), but x = 3 would have to be done as x.val = 3

更多回答（1 个）

Aaron Kaw
Aaron Kaw 2023-11-6
编辑：Aaron Kaw 2023-11-6
Try
x = myDouble(2,'string')
double(x)
I like to also add the following non-static method to my double subclasses:
function value = double(instance)
value = builtin('double', instance);
end
so that I can do
y = myDouble(2, 'string').double
if I only cared about the double value the class outputed for the particular usage of myDouble.

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