MATLAB: About function in methods of a class

classmethodsoop

Hi guys, I'm doing a project.
To use function in methods of one of my class I defined, I made this one :
function [y, Fs] = getRandomMusic(feeling)
    path_name = strcat('C:\Users\Jack\Desktop\music','\',feeling);
    music_lists = dir(path_name);
    music_number = length(music_lists);
    
    ran_music_number = randi(music_number);
    while ran_music_number < 3
        ran_music_number = randi(music_number);
    end
    
    file_name = strcat(path_name,'\',music_lists(ran_music_number).name);
    [y, Fs] = Audioread(file_name, native);
end
This is the function when input "feeling", then it returns [y, Fs] of randomly selected from the "feeling" folder.
But when I rud the main MATALB file to use this function, it makes an error messgae like this :
Check the function 'getRandomMusic' for missing arguments or invalid argument data types. (It's not official message cuz my mother tongue isn't english)
Can anyone suggest something to me?
Thanks!

Best Answer

If getRandomMusic is a non-Static method of a class (which I'll call iPod just to have some way to refer to the class) then at least one of the inputs to getRandomMusic must be an iPod object. If you try to call it without at least one iPod object, MATLAB won't know to what getRandomMusic refers.
You could make feeling an iPod object, or you could have getRandomMusic accept two inputs (one an iPod object and one a char vector or string, based on the context.)
p = iPod;
[y, Fs] = getRandomMusic(p, 'happy');
Other options include making getRandomMusic a Static method of the iPod class, in which case you would need to call it using the class name:
[y, Fs] = iPod.getRandomMusic('happy');
or turning getRandomMusic into a function rather than a method. If it's only intended to be called from within methods of the iPod class it could be a class-related function defined in the classdef file but after the end keyword associated with the classdef keyword. If you intend it to be called from outside the class as well I'd define it as a regular function in its own file.
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