I cannot figure out how to add a method with a parameter of type double

Question

I need to do the following: "We need to figure out the tax amount when the tax percentage is 7.5 percent. Call the method calculateTaxes on the variable item and assign the result to a new variable named taxes."

I have done the code that you see, but the coding challenge says that I need to add a method named calculateTaxes with a parameter named Percentage of type double. I'm not sure what I am doing wrong. If you could please help, that would be great!

struct.swift

struct Expense {
    var description: String
    var amount: Double = 0.0

    init (description: String) {
        self.description = description
    }

    func calculateTaxes(parameter: Double, percentage: Double) -> Double  {
    return (self.amount * (parameter/100))

    }

 }

 var item = Expense(description: "Gas price")
 item.amount = 100

 var taxes = item.calculateTaxes(percentage)




    // add the calculateTaxes method here
    // it should accept only one parameter named 'percentage' of t

Answer 1 · 2015-07-01T07:18:36Z

July 1, 2015 7:18am

Hello Austin :

What’s is important here is that you are very close and seem to understand most of the concept of accessing a structs properties and such with the dot syntax.

Please see the 2 codes below, the first one is yours, and I will highlight with comments some changes, and the second code will give you those changes and the answer to your challenge.

struct Expense {
    var description: String
    var amount: Double = 0.0

    init (description: String) {
        self.description = description
    }

   /* 
    The challenge says to create a method with a parameter named 
    “percentage” of type double. As you can see on your method,
     you have an extra parameter.
     (parameter: Double) should not be in the method’s signature.
   */

    func calculateTaxes(parameter: Double, percentage: Double) -> Double  {
    return (self.amount * (parameter/100))

    }

 }

 var item = Expense(description: "Gas price")
 item.amount = 100
    /*
    Since you have an extra parameter not required by the challenge, 
    then you don’t need to add (percentage) here. Instead use a 7.5 which is 
    what the challenge wanted for taxes. 
    */


 var taxes = item.calculateTaxes(percentage)

This is what you want :

struct Expense {
    var description: String
    var amount: Double = 0.0

    init (description: String) {
        self.description = description
    }

    func calculateTaxes(percentage: Double) -> Double {
    return (self.amount * (percentage / 100))

    }

}

var item = Expense(description: "Gas Price" )
item.amount = 100

var taxes = item.calculateTaxes(7.5)

/* 
  You may be wondering, “Why did you not put item.calculateTaxes(percentage: 7.5)”
  This is because the name of the parameter is not explicit. If you wanted to make
  it explicit, you had to NAME your external parameter.

  Examples:

  on swift 1.2 
  func calculateTaxes(#percentage: Double) -> {}

  on swift 2.0
  func calculateTaxes(percentage percentage: Double) -> {}

*/

I hope that helps, if you have any other questions please ask :)

Happy learning

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Austin Wyatt

Austin Wyatt

I cannot figure out how to add a method with a parameter of type double

1 Answer

Jhoan Arango

Jhoan Arango