Generic get/set methods for class properties

Question

Neil Casson 2021-6-30

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编辑： Benjamin Kraus 2023-4-27

I've got some classes with loads of properties, all of which need a get/set method. Apart from the property names, the get/set methods are all identical. Is there any way to write a single generic get and set method that can parse the property name and act accordingly?

So for example, if my class currently looks something like this:

classdef testClass < handle
    
    properties(Access = private)
        privateProp1
        privateProp2
    end
    
    properties(Dependent)
        Prop1
        Prop2
    end
    
    methods
       
        function val = get.Prop1(obj)
            val = obj.privateProp1;
        end
        
        function val = get.Prop2(obj)
            val = obj.privateProp2;
        end
    end
    
end

Is there some way to just have a single version of the get method? In my head it would look something like this, but obviously this doesn't work:

        function val = get.(propname)(obj)
            val = obj.(['private', propname]);
        end

It needs to work with dot notation, e.g.:

myClass = testClass;
var = testClass.Prop1;

I'm just trying to avoid defining dozens of near identical get and set methods, but I suspect there is no way round this.

Thanks

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Answer 1

Steven Lord 2021-6-30

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If all you're doing in your generic get and set methods are accessing the properties, you don't really need them. Just use dot indexing like this and the normal indexing will do the right thing:

myClass = testClass;
var = myClass.Prop1;

If you do need something like this to work:

get(myClass, 'Prop1')

have your handle class inherit from the matlab.mixin.SetGet class.

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Neil Casson 2021-6-30

I haven't shown it in the example, but in the actual class I'm writing the get method does some conversions of data types and such like, so I can't really dispense with the get methods.

Using the matlab.mixin.SetGet approach also won't work, as it needs to be compatible with dot indexing

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Answer 2

Marco 2023-4-27

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You can try to inherit from both handle class and matlab.mixin.SetGet class.

classdef myClass < handle & matlab.mixin.SetGet

It worked for my purpose, hope it could help somebody.

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Answer 3

Benjamin Kraus 2023-4-27

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编辑：Benjamin Kraus 2023-4-27

You may be able to do something like this by implementing subsref (and/or subsasgn), but it isn't for the faint of heart.

Using subsref and subsasgn you can redifine how your object responds to all types of references, including the "dot assignment" and "dot references" (and parentheses, and curly braces).

However, by overloading subsref you are taking over all references (dot, parentheses, and braces), and handling all cases can be a challenge.

I'd start by checking out the doc page Code Patterns for subsref and subsasgn Methods.

However, I would caution that, once you look at the sample code, you may just choose to switch back to copy/pasted get and set methods.