MATLAB: Argin for a class method

method classnargin

http://www.mathworks.es/help/techdoc/ref/nargin.html :

fx = 'addme';  % the name of a function
nargin(fx) %returns the number of input arguments
ans =
     2

I want to use "nargin" for a class method But I get an error.

fx='classname.methodname'
nargin(fx)
Error using ==> nargin
Not a valid M-file.

I want to call nargin from outside the class, for example in command window. What can I do?

Best Answer

NARGIN does not currently (as of R2012a) work on class methods. However, you might be able to get the information you want by inspecting the metaclass for your class with the ? operator. For example, try:

metaInfo = ?classname
methodInfo = metaInfo.MethodList
firstMethodInputs = methodInfo(1).InputNames

For a given method, you could find the MethodList entry with a matching name and then count InputNames to get the number of inputs. You'd also want to check if the last input is named varargin.

Related Solutions

MATLAB: Setting object properties without returning the object using obj = obj.thefun(obj,argin)

What you want is a handle class. See Comparison of Handle and Value Classes for more details.

Note that if you're not proficient with matlab and just a beginner with OOP, I wouldn't recommend you start writing handle classes until you've mastered value classes. Handle classes should be the exception rather than the norm in matlab.

MATLAB: How do we find the input arguments required by a handle class constructor

It sounds like the problem has already been resolved and as Adam said, the easiest is to look at the function definition.

If, for some reason, that's not possible, you can use the methods function (for display at the command line) with the -'full' option, or the methodsview function (for display in a separate window) to see the list of all the methods of the class and their inputs and outputs.

methods('classname', '-full')
%or
methodsview('classname')

If even more details are needed, you can also use introspection classes such as meta.class and meta.method.

%demo for class string
>> mc = meta.class.fromName('string');
>> mm = mc.MethodList(strcmp({mc.MethodList.Name}, 'string'))  %find constructor in method list and display properties
mm = 
  method with properties:
                   Name: 'string'
            Description: ''
    DetailedDescription: ''
                 Access: 'public'
                 Static: 0
               Abstract: 0
                 Sealed: 0
     ExplicitConversion: 0
                 Hidden: 1
             InputNames: {'rhs1'}
            OutputNames: {'lhs1'}
          DefiningClass: [1×1 meta.class]

Interestingly, the string constructor is hidden.

Best Answer

Related Solutions

MATLAB: Setting object properties without returning the object using obj = obj.thefun(obj,argin)

MATLAB: How do we find the input arguments required by a handle class constructor

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