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iOS Object-Oriented Swift 2.0 Complex Data Structures Custom Initializers

Posted by Terrell Winston
Terrell Winston
Courses Plus Student 1,811 Points

someone guide me down the write path i don"t know how i got lost

its saying don't use member initializers but why though

structs.swift 
struct RGBColor {
    let red: Double
    let green: Double
    let blue : Double
    let alpha: Double
    let description : String
    init(red: Double, green: Double, blue: Double, alpha: Double, description: String)
        { self.red = 86.0
            self.green = 191.0
            self.blue = 131.0
            self.alpha = 1.0
            self.description = "red, green, blue, alpha"
    }

below

1 Answer

Steve Hunter
Steve Hunter
57,712 Points

Hi Terrell,

First up, the initializer doesn't set the values of the member variables to hard-coded numbers - the initializer takes the values passed into it, and applies those to the member variables.

Taking that first step, the init method looks like:

init(red: Double, green: Double, blue: Double, alpha: Double){
  self.red = red
  self.green = green
  self.blue = blue
  self.alpha = alpha
}

We're not done yet, though!

The description member variable is created inside the init method. It uses the values passed in to generate a string using string interpolation. Adding that gives us:

init(red: Double, green: Double, blue: Double, alpha: Double){
  self.red = red
  self.green = green
  self.blue = blue
  self.alpha = alpha
  self.description = "red: \(red), green: \(green), blue: \(blue), alpha: \(alpha)"
}

I hope that makes sense!

Steve.

steve kevin arias serrano
steve kevin arias serrano
9,037 Points

why you don at description to init like alpha:Double

Steve Hunter
Steve Hunter
57,712 Points

You don't add description in the init`` method as a parameter as it can be generated by using the other parameters. The code can construct thedescription``` from the other parameters so let's not ask the user to do it!

The struct is complete once the init method has run as all its stored properties have a value. Those values don't have to come from outside of the struct - there's nothing wrong with calculating some or all from existing information.