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OOP: How to let a bunch of methods behave differently depending in the type of input?

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Let's imagine we have a Class called OOP_Base and lots of subclasses like "OOP_Mult5" that implement the "Apply" Method defined "abstract" in the OOP_Base class.
I like to convert accidental char inputs for all those classes to double. I don't want to implement a isa(in,'char') in all hundred methods "OOP_Mult5" and so on.
Is it possible to put the "isa()"-query and a str2num() if the input is char in the OOP_Base for all subclasses?
% OOP_Base:
classdef OOP_Base
methods (Abstract = true)
result = Apply(in)
end
end
classdef OOP_Mult5 < OOP_Base
methods (Static = true)
function result = Apply(in)
result = 5*in;
end
end
end
P.S.: This is just an example to illustrate my problem. In reality I have to deal with lots of filters that should work with a special "Image"-class but also with simple R,G,B vectors.
Thank you very much in advance for your help,
Jan

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Accepted Answer

Matt J
Matt J on 9 Oct 2012
Edited: Matt J on 9 Oct 2012
Instead of making Apply() abstract, make it call abstract functions:
classdef OOP_Base
methods result=Apply(in)
if ischar(in), in=str2num(in); end
result=ApplyMain(in);
end
methods (Abstract = true)
result = ApplyMain(in)
end
end
classdef OOP_Mult5 < OOP_Base
methods (Static = true)
function result = ApplyMain(in)
result = 5*in;
end
end
end

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More Answers (1)

Jan Froehlich
Jan Froehlich on 13 Oct 2012
Hi Matt,
thank you very much, I had to play around a bit with your code but now it works fine:
classdef A
methods
function Apply(this,in)
disp('In abstract parent');
if isa(in,'char'), in=str2double(in); disp('Is char'); end
if isa(in,'double'), disp('Is double'); end
disp(mfilename('class'))
this.ApplyWorker(in);
end
end
methods(Abstract,Static)
ApplyWorker(in);
end
end
classdef B < A
methods (Static = true)
function ApplyWorker(in)
disp('In B');
disp(in*5);
end
end
end
classdef C < A
methods (Static = true)
function ApplyWorker(in)
disp('In C');
disp(in*10)
end
end
end
Typing:
clear classes
b = B;
c = C;
b.Apply(2)
b.Apply('2')
c.Apply(2)
c.Apply('2')
results in:
In abstract parent
Is double
A
In B
10
In abstract parent
Is char
Is double
A
In B
10
In abstract parent
Is double
A
In C
20
In abstract parent
Is char
Is double
A
In C
20
Thanks again for your fast help!
Jan

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