Cannot retrieve argument list from a class constructor with arguments checking

I've the following class:

classdef Main

%MAIN Summary of this class goes here

% Detailed explanation goes here

properties (Access = private)

logger;

options;

end

methods (Access = public)

function this = Main(options, logger)

%MAIN Construct an instance of this class

% Detailed explanation goes here

this.logger = logger;

this.options = options;

end

end

end

I want to retrieve the list of arguments of the constructor, and I do this way:

c = ?Main;

c.MethodList.InputNames

I obtain

ans =

2×1 cell array

{'options'}

{'logger' }

And everything is ok.

Now I also want to add a check on the arguments, to be sure that they are of the correct type. So I've updated my class this way:

classdef Main% < App.Interfaces.Component

%MAIN Summary of this class goes here

% Detailed explanation goes here

properties (Access = private)

logger;

options;

end

methods (Access = public)

function this = Main(options, logger)

%MAIN Construct an instance of this class

% Detailed explanation goes here

arguments

options (1, 1) App.Options

logger (1, 1) App.Logger

end

this.logger = logger;

this.options = options;

end

end

end

But now, If I try to re-run the code for retrieving the arguments, I obtain

ans =

1×1 cell array

{'varargin'}

Adding the check does not allow me to retrieve the arguments anymore, because I obtain only varargin.

Why this happens? Is there a way to add the arguments check and retrieve correctly the names of the constructor arguments anyway?

Answer 1

[Venkat Siddarth Reddy]

Hi Daniele,

When you add the "arguments" block to your constructor, MATLAB treats the input arguments as a single "varargin" cell array for validation purposes. This is why you see "{'varargin'}" instead of the individual argument names.

Unfortunately, I don't see a way from the properties of "Main" class meta class to determine the constructor argument names. The following are the properties of the "Main" class meta class.

className = "Main";
mc = matlab.metadata.Class.fromName(className)

mc = 
  Class with properties:

                     Name: 'Main'
              Description: 'Summary of this class goes here'
      DetailedDescription: '    Detailed explanation goes here'
                   Hidden: 0
                   Sealed: 0
                 Abstract: 0
              Enumeration: 0
          ConstructOnLoad: 0
         HandleCompatible: 0
          InferiorClasses: [0x1 matlab.metadata.Class]
                Namespace: [0x0 matlab.metadata.Namespace]
                  Aliases: [0x1 string]
     RestrictsSubclassing: 0
             PropertyList: [2x1 matlab.metadata.Property]
               MethodList: [2x1 matlab.metadata.Method]
                EventList: [0x1 matlab.metadata.Event]
    EnumerationMemberList: [0x1 matlab.metadata.EnumerationMember]
           SuperclassList: [0x1 matlab.metadata.Class]

ctor = mc.MethodList(strcmp({mc.MethodList.Name}, className))

ctor = 
  Method with properties:

                   Name: 'Main'
            Description: 'Construct an instance of this class'
    DetailedDescription: '    Detailed explanation goes here'
                 Access: 'public'
                 Static: 0
               Abstract: 0
                 Sealed: 0
                 Hidden: 0
             InputNames: {'varargin'}
            OutputNames: {'this'}
          DefiningClass: [1x1 matlab.metadata.Class]

In this scenario, I would recommend creating a custom method in the class, which has explictly stated information about the argument types:

methods (Access = public, Static)
    function argsInfo = getConstructorArgs()
        argsInfo = struct('options', 'App.Options', 'logger', 'App.Logger');
    end
end

I hope it helps!

Regards

Venkat Siddarth V

[Daniele Lupo]

I see... I'll check for the workaround then, thanks.