how do proceed? I'm stuck at cause I'm not able to apply. what concept am i lacking? please help

Question

In the editor, I’ve declared a struct named RGBColor that models a color object in the RGB space.

Your task is to write a custom initializer method for the object. Using the initializer assign values to the first four properties. Using the values assigned to those properties create a value for the description property that is a string representation of the color object.

For example, given the values 86.0 for red, 191.0 for green, 131.0 for blue and 1.0 for alpha, each of the stored properties should hold these values and the description property should look like this:

"red: 86.0, green: 191.0, blue: 131.0, alpha: 1.0"

Note: Init methods typically list parameters in the same order of property declaration. For this task, stick to the order red,green,blue,alpha.

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) {
  self.red = 86.0
  self.green = 191.0
  self.blue = 131.0
  self.alpha = 1.0

  let description = return "red:"
    // Add your code below
}

Answer 1 · 2016-10-27T15:45:37Z

October 27, 2016 3:45pm

HI Aditya,

Have a read through this thread which might help you out.

A couple of things. First, you don't want to hard-code the number values; they are what get passed into the init method. So, self.red = 86.0 should be self.red = red - the second red is passed in by the user; they want to be able to create a struct containing any color, right?

Then, inside the init method, build up the description string, as in the question, using string interpolation. Something like self.description = "red: \(red), green: \(green), blue: \(blue), alpha: \(alpha)".

I hope that helps,

Steve.

Answer 2 · 2016-10-28T09:39:35Z

October 28, 2016 9:39am

Hi Aditya,

The init method is used to make sure all stored properties are given a value as the instance of the struct is created.

Each property can be set inside init directly, or the uer can pass a value in as the instance is created. Let's look at the directly set way first. This is what you set off doing in your code at the beginning of this thread. Each value for red, green etc. is set inside the init method.

init() {
  self.red = 86.0
  self.green = 191.0
  self.blue = 131.0
  self.alpha = 1.0

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

In this way, the init method takes no parameters; it doesn't need them as it will do nothing with them. All stored properties are set wthin the init method, so the compiler is happy. BUT every struct is identical and cannot be changed. Obviously, this is not what we want.

So let's look at how else this can be done. This example is the answer to the challenge. The challenge wants a user to be able to create a struct to represent any color. While there are no bounds-checks or tests in this example, let's assume that the user won't pass in a number outside the range 0 - 255, as that's what the RGBA representation is trying to achieve.

The color representation is determined by the four constituents, RGB & A. The description stored property is made up of a string with the other four properties' values interpolated into it. The user doesn't need to present any additional information to construct the string correctly - so the user only needs to provide the RGB & A values. So, the init method now takes four parameters; red, green, blue and alpha but the struct has five stored properties. THis is fine, as long as the init method sets all five properties to contain a value, then the compiler is happy. The init method has enough information to set all five values even though only four are being passed in - the fifth is made up of the other four and no other information:

    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)"
    }

The compiler wants to have all five properties set using the init method; that' done, so it is happy. The user wants to be able to create a representaion of any color by passing in chosen values for red, green, blue and alpha; that's done so the user is happy too. A color representation can be created like:

let someColor = RGBColor(red: 21.2, green: 32.3, blue: 43.5, alpha: 65.7)

The struct will be created, inserting thoe values in to each of the red, green, blue and alpha stored properties. The description will look like:

"red: 21.2, green: 32.3, blue: 43.5, alpha: 65.7"

I hope that helps explain why an init method is used and why is in't necessary to pass every stored property into the init method. The init method must set a value for all stored properties but those properties can either be hard coded or made up of other parameters. So, in the above example, there is no need for the user to pass in a string for the description propery as it could be correctly created without any user-input.

Steve.

Answer 3 · 2016-10-28T08:52:52Z

October 28, 2016 8:52am

thank you very much steve but that thread gave me a doubt which i did not realise myself and now I'm a bit confused; why do we use init and why did we not put description in init?

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Aditya Gawade

Aditya Gawade

how do proceed? I'm stuck at cause I'm not able to apply. what concept am i lacking? please help

3 Answers

Steve Hunter

Steve Hunter

Steve Hunter

Steve Hunter

Aditya Gawade

Aditya Gawade

Steve Hunter

Steve Hunter

Aditya Gawade

Aditya Gawade