Double naming a variable/type

Hi Jean-Emrick Rioux,

Firstly, I've fixed up your code formatting so I recommend you have a read of Posting Code to the Forum for future knowledge .

Ok, so let's break this down, in Swift constructors for structs and/or classes have a requirement that you must specify the parameter name when creating a new instance of the object.

What does that mean and what is a parameter name?

In Swift there is a core concept which is when creating a new instance of an object that you need to specify the parameter name first which is the name given in the struct and/or class init function, however if we don't specify a custom init function the names of the stored properties are used instead.

Example 1

Without a custom constructor.

struct Person {
  var firstName: String
  var lastName: String
}

var john = Person(firstName: "John", lastName: "Doe")

Example 2

With a custom constructor.

struct Person {
  var firstName: String
  var lastName: String

  init(first: String, last: String) {
    self.firstName = first
    self.lastName = last
  }
}

var john = Person(first: "John", last: "Doe")

So what's the difference, well back to your original question we can see that when creating a new instance of the Person struct it referenced the name of the stored properties when entering the arguments, whereas in the second example we've switched this to a custom constructor where the arguments now use first and last as the labels.

Ok, what's a parameter label, where'd that come from?

Well, they've been there the whole time. In Swift only constructors as I said have a requirement that you need to specify the parameter name before the value, these are called parameter labels as they tell the Swift compiler which value is for which parameter.

Parameters labels aren't just available to constructors either, you can use them anywhere but rather than explaining it all over again have a read of this post as it explains more about them in detail.

Wrapping up

• When creating a new instance of a struct or class the parameter name is required
• Parameter labels can be used on custom functions and methods
• Parameter labels aren't the same as parameter values
• Keep practicing

Hope that helps.