MATLAB: Argument in function from class

classMATLABoop

I have a question about the function in the class. I have main.m and my_class.m . my_class has following function,
classdef my_class
  ... 
  function 
       [x,y,z,w] = get_File(pathname,filename)
       completename = fullfile(pathname,filename);
       data = load(completename);
       x = data(:,1);
       y = data(:,2);
       .....
  end
end
here simply trying to load the file from pathname and filename as input. But when main.m tries to include this function by
pathname = 'my pathname';
filename = 'my filename';
obj = my_class;
[a,b,c,d] = obj.get_File(pathname,filename);
error shows up as follows
Error using my_class/get_File
Too many input arguments.
Error in Untitled (line 4)
[a,b,c,d] = obj.get_File(pathname,filename);
Seems this error will disappear if I set the function as
function 
     [x,y,z,w] = get_File(~,~) %<--- here its changed
     pathname = 'my pathname';
     filename = 'my filename';
     completename = fullfile(pathname,filename);
     data = load(completename);
     x = data(:,1);
     y = data(:,2);
     .....
end
and include in main.m like
obj = Tomography_Tool;
[a,b,c,d] = obj.get_File;
can anybody explain why I got the error and disappear by this modification?
thank you for your help,

Best Answer

When you call the method like:
 [a,b,c,d] = obj.get_File(pathname,filename);
you're calling it with THREE input arguments, not two. As stated in the documentation, these two commands are equivalent in most circumstances.
 [a,b,c,d] = obj.get_File(pathname,filename);
 [a,b,c,d] = get_File(obj,pathname,filename);
They even have the same number of characters, though the first has a period and the second a comma.
So either define your function differently:
function [x,y,z,w] = get_File(obj,pathname,filename)
or, if get_File doesn't actually use the object (the section you quoted doesn't, though perhaps part of the code you snipped out does) make it a static method or perhaps a plain old function.
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