CODEWITHSUNDEEP
swiftint
SIDDHARTH MEHTA
SIDDHARTH MEHTA

Reputation: 111

Difference between Int() and :Int in Swift

I'm new to Swift and I am confused about the following:

In the lines Int(something) and var x :Int = something, what is the difference between Int() and :Int?

Upvotes: 1

Views: 2454

Answers (2)

Antonio
Antonio

Reputation: 72780

From a pure language perspective, the correct way to assign a value to an integer (or other numerical types) variable is:

let num = Int(16)

or any of its variants.

However Swift implements some syntactic sugar to make that less verbose - thanks to which you can rewrite the above statement as:

let num = 16

which is equivalent to:

let num: Int = 16

(thanks to type inference)

This is possible because the Int type implements the IntegerLiteralConvertible protocol, and by doing that the compiler is able to translate an integer literal into an initializer invocation.

There are several other protocols like that, for string, array, float, etc.

If you want to know more, I recommend reading Swift Literal Convertibles at NSHipster.

If you are wondering if you can do that on your own classes/structs, the answer is yes - you just have to implement the protocol corresponding to the literal type you want to use.

Upvotes: 1

vadian
vadian

Reputation: 285250

In fact var x = Int(something) and var x : Int = something is exactly the same.

Unlike in Objective-C where int is a scalar type Int in Swift ist a struct and structs must be initialized.

The former syntax is an explicit call of the initializer, the latter an implicit call by assigning the value

Upvotes: 4

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