Empty array of class objects from string name of class
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If I have a class called SomeClass, I can create an empty array of SomeClass using:
arr = SomeClass.empty
Is there a way to create an empty array if I only have the character string "SomeClass".
5 comentarios
Stephen23
el 18 de Ag. de 2018
Editada: Stephen23
el 18 de Ag. de 2018
Although slightly different from the usual approach, this will have almost all of the same disadvantages as the usual dynamic variable names that some beginners like to use to force themselves into writing slow, complex, buggy code:
Respuestas (3)
Guillaume
el 18 de Ag. de 2018
"Those familiar with Matlab will know that this will not work"
This.elements(end+1) = obj;
Indeed, but the semantically equivalent
This.element = [This.element, obj];
will. No need to test for emptiness.
Image Analyst
el 17 de Ag. de 2018
Doing this - making variables named from strings - is a bad idea. I mean, just how would you refer to that variable later? How would you use it if you don't know the variable name before run-time? See this link
2 comentarios
Steven Lord
el 17 de Ag. de 2018
It's extremely easy to come up with a piece of text that is not a valid class name but if used with Image Analyst's suggestion would do various nasty things. I'm not going to post one because I don't want people to get angry if they closed their MATLAB session by running the example.
If you must use this approach to run code from your users, make absolutely sure to sanitize your inputs. Use meta.class.fromName to validate that the class name you've been given is an actual class. Here's one that does not exist:
name = 'thisClassDoesNotExist';
if isempty(meta.class.fromName(name))
fprintf('The class %s does not exist!\n', name);
else
fprintf('Class name %s exists, you may create an empty.\n', name);
end
Here's one that does.
name = 'table';
if isempty(meta.class.fromName(name))
fprintf('The class %s does not exist!\n', name);
else
fprintf('Class name %s exists, you may create an empty.\n', name);
end
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