Swift learning-a swift tour Function

Functions and closures functions and closures)

Use of functions

There is a significant difference between Function Definition and OC in swift. Use func to define the function, define the number and type of struct in brackets, and use-> to define the type of return value.

func greet(name: String, day: String) -> String {    return "Hello \(name), today is \(day)."}greet("Bob", "Tuesday")

Use a single tuple () to return multiple return values

func getGasPrices() -> (Double, Double, Double) {    return (3.59, 3.69, 3.79)}getGasPrices()

The function can also have a variable number of shards (in this case, it is better to input an array). Note that there are three points...

func sumOf(numbers: Int...) -> Int {    var sum = 0    for number in numbers {        sum += number    }    return sum}sumOf()sumOf(42, 597, 12)

Functions can also be nested. nested functions can be used to explain external function variables.

func returnFifteen() -> Int {    var y = 10    func add() {        y += 5    }    add()    return y}returnFifteen()

New Feature: swift defines a function as a type, that is, it can define a function variable. The return value of a function can be a function.

func makeIncrementer() -> (Int -> Int) {    func addOne(number: Int) -> Int {        return 1 + number    }    return addOne}var increment = makeIncrementer()increment(7)

A function can use another function as its limit number.

func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool {    for item in list {        if condition(item) {            return true        }    }    return false}func lessThanTen(number: Int) -> Bool {    return number < 10}var numbers = [20, 19, 7, 12]hasAnyMatches(numbers, lessThanTen)

Use of closures Closure

A function is actually a closure. You can define a closure without a name. You only need to include the closure with braces, use in to divide variables and return values (in fact, similar to block in OC)

numbers.map({    (number: Int) -> Int in    let result = 3 * number    return result    })

You can omit the number of records and return values to make the closure above a more simple introduction. Just one closure of a statement directly returns the running result of this statement.

numbers.map({ number in 3 * number })

You can also write a closure behind the brackets.

sort([1, 5, 3, 12, 2]) { $0 > $1 }

Next, let's talk about objects and classes.