MATLAB: How to call a function which I have defined within a class

classmethodoop

I'm trying to learn how to use classes in Matlab, having never used them in any language before, so apologies if this is a bit basic.

I have defined a class called car, with the properties of colour, type, serial number and speed, with a function to change the speed.

classdef car <handle
   properties
      colour
      type
      speed
   end 
   properties (SetAccess = private)
      SerialNumber
   end
   methods
       function faster(obj, v)
           obj.speed = obj.speed + v;
       end
   end
end

In another script I can type

car.colour = "red",

and when I disp(car), the class has the property colour with label "red". When I call faster(100) however, instead of setting car.speed=100, it throws the error

Check for missing argument or incorrect argument data type in call to function 'faster'.

I built the class and method using the same sort of code structure as in this question:

https://www.mathworks.com/matlabcentral/answers/395472-how-to-call-a-method-from-a-class-called-a-within-another-method-from-a

where the user seemed to not have the issue I do. I'm not sure where I'm going wrong – my function seems like it should work. Can anybody point me in the right direction?

Best Answer

This question has now been answered on Stack Overflow:

https://stackoverflow.com/questions/65038867/matlab-how-do-i-call-a-function-which-i-have-defined-within-a-class.

Related Solutions

MATLAB: How can i call class from a function

You should really have a look at the documentation of how you write classes in Matlab, starting for example here.

With the code below in a file called 'car.m', you can call aCar=car(3);aCar.showSpeed and it will disp the speed.

classdef car
    properties
        speed
    end
    methods
        function obj = car(set_speed)
            if nargin>0
                obj.speed=set_speed;
            else
                obj.speed=0;
            end
        end
        function obj = setSpeed(obj,set_speed)
            obj.speed=set_speed;
        end
        function showSpeed(obj)
            disp(obj.speed)
        end
    end
end

MATLAB: Object composition and property updating

You should think about whether the tire needs to be exposed as a public property on the car, or whether it can be private. In any case, one approach for your problem is to use SET methods for properties. An example is below, where the car has a public color, which when set updates the car's bodyColor and its tire's paintColor.

 classdef Car < handle
    properties(Dependent)
        color;
    end
    properties(Access = private)
        tire;
        bodyColor;
    end
    methods        
        function set.color(this, v)
            this.bodyColor = v;
            this.tire.paintColor = v;
        end
        function v = get.color(this)
            v = this.bodyColor;
        end
        function obj = Car
            obj.tire = Tire;
            obj.color = 'black';
        end
    end
 end
 classdef Tire < handle
    properties
        paintColor = 'black'; 
    end
 end

Using that approach, the tire doesn't even need to know what car it is attached to. Now if it is the case that you need to have the tire exist separately from the car, another approach would be to have the tire's color dependent upon the car it is attached to:

 classdef Car < handle
    properties(Dependent)
        color;
    end
    properties(Access = private)
        tire;
        bodyColor;
    end
    methods        
        function set.color(this, v)
            this.bodyColor = v;
        end
        function v = get.color(this)
            v = this.bodyColor;
        end
        function obj = Car(aTire)
            obj.tire = aTire;
            obj.tire.car = obj;
            obj.color = 'black';
        end
    end
 end
 classdef Tire < handle
    properties
        car;
    end
    properties(Dependent, SetAccess = private)
        paintColor = 'black'; 
    end
    methods
        function v = get.paintColor(this)
            v = this.car.color;
        end
    end
 end

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