Passing an object from a method function to another function

I'm having trouble passing an object from a method function to another function.

I want to pass the obj.federaltax and obj.provincialTax to my calc_totalTax func to calcluate the totalTax but all i'm getting is an empty value for totalTax.

classdef calcTax
   properties
       income = input('enter annual income: ');
       federalTax;
       provincialTax;
       totalTax;
   end
   
       function obj = calc_federalTax(obj)
           if obj.income <= 46605
                obj.federalTax = obj.income*15/100;
           else 
              obj.federalTax = obj.income*15/100; 
           end
        end
      
       function obj = calc_provincialTax(obj)
           if obj.income <= 42960
               obj.provincialTax = obj.income*5.05/100;
        
           else
               obj.provincialTax = obj.income*9.15/100;
           end            
       end
       
       function obj = calc_totalTax(obj)
            obj.totalTax = obj.provincialTax + obj.federalTax
            disp(totalTax)
       end
       
   end
      
end

Answer 1

[Steven Lord]

Nowhere in the code did you call your federal and provincial tax calculation methods. There are at least two possible solutions:

• Call those calculation methods in your total tax calculation method.

       function obj = calc_totalTax(obj)
            obj = calc_provincialTax(obj);
            obj = calc_federalTax(obj);
            obj.totalTax = obj.provincialTax + obj.federalTax
            disp(totalTax)
       end

• Make the three tax-related properties Dependent properties whose values are computed when you ask for them using the value of the non-Dependent income property. See this documentation page for a short example. In the example the Balance property is not stored in the object; it's computed using the values of the DollarAmount and Current properties that are stored in the object.

[mzw]

My bad I forgot to include my main program code -

    o = calcTax; 
    o.calc_federalTax; 
    o.calc_provincialTax;
    o.calc_totalTax;

[Steven Lord]

That code executes the calc_federalTax method on the copy of the object o that was passed into it, updates the properties of that copy, then promptly throws that copy in the trash because you don't assign the output of the function call to a variable.

Now that I think about it a bit more carefully, I'm not sure it make sense to store the value of the calculated tax as part of the object. I'd probably do something like:

classdef calcTax
   properties
       income = input('enter annual income: ');
   end
   % I assume you intended to have a methods keyword here
   % lined up with the next-to-last end keyword in this code
       function calculatedTax = calc_federalTax(obj)
           if obj.income <= 46605
                calculatedTax = obj.income*15/100;
           else 
              calculatedTax = obj.income*15/100; 
           end
        end
      
       function calculatedTax = calc_provincialTax(obj)
           if obj.income <= 42960
               calculatedTax = obj.income*5.05/100;
        
           else
               calculatedTax = obj.income*9.15/100;
           end            
       end
       
       function calculatedTax = calc_totalTax(obj)
            calculatedTax = obj.calc_provincialTax + obj.calc_federalTax;
            disp(calculatedTax)
       end
       
   end
      
end

Call it:

myTaxForm = calcTax();
myTotalTax = calc_totalTax(myTaxForm) % or
myTotalTax = myTaxForm.calc_totalTax;

If you do need to update the object, either call the calc_*Tax methods with an output or make it a handle class. Using your original class the former would be:

o = calcTax; 
o = o.calc_federalTax; 
o = o.calc_provincialTax;
o = o.calc_totalTax;

For the latter make it a handle class and eliminate the output arguments from each of your methods. Search the documentation for "handle class" for more information.

classdef calcTax < handle
    ...
    function calc_federalTax(obj)
    ...
    end
    ...
end