Functions
Functions are a special type of closures. Functions are first-class types, so a function can be passed in as a parameter to another function. Also, a function can return another function. Functions that belong to a struct, class, or enum are methods.
- Function with type
() -> () - Function with type
(String) -> () - Function with type
(Int, Int) -> (Int) - Function with a default parameter value
- Function that takes in another function as a parameter
- Function that returns a function
- Further reading
Function with type () -> ()
This function takes no parameters, and returns nothing.
func greet() {
print("Hello")
}
greet() // "Hello"
Function with type (String) -> ()
This function takes one parameter, a String, and returns nothing.
func greet(person: String) {
print("Hello \(person)")
}
greet(person: "Aliya") // "Hello Aliya"
Function with type (Int, Int) -> (Int)
This function takes two parameters, both Ints, and returns an Int.
func multiply(x: Int, y: Int) -> Int {
return x * y
}
print(multiply(x: 5, y: 6)) // 30
Function with a default parameter value
This function takes two parameters, both Ints, and returns an Int.
func greet(person: String = "guest") {
print("Hello \(person)")
}
greet() // Hello guest
greet(person: "Aliya") // Hello Aliya
Function that takes in another function as a parameter
The function perform has type ((Int, Int) -> Int, Int, Int) -> Int.
func multiply(x: Int, y: Int) -> Int {
return x * y
}
func perform(fn: (Int, Int) -> Int,
a: Int,
b: Int) -> Int {
return function(a, b)
}
let result = perform(fn: multiply,
a: 5,
b: 6)
print(result) // 30
Function that returns a function
The function operation has type () -> (Int, Int) -> Int.
func multiply(x: Int, y: Int) -> Int {
return x * y
}
func operation() -> ((Int, Int) -> Int) {
return multiply
}
let myOperation = operation()
let result = myOperation(5, 6)
print(result) // 30
