Closure, Higher-order function in Swift
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This document discusses closures and higher-order functions in Swift. It provides examples of using closures as parameters, including sorting an array by passing a closure. It also gives examples of common higher-order functions like map, filter and reduce. Map transforms elements by applying a closure, filter filters elements by a closure condition, and reduce combines elements using a closure.
![CLOSURE AS PARAMETER
func sorted(by areInIncreasingOrder: (E, E) -> Bool) -> [E]
(Type, Type) -> Type](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-7-320.jpg)
![CLOSURE
func backwards(left: String, right: String) -> Bool {
print("(left) (right) ")
return left > right
}
let names: [String] = ["hana", "eric", "yagom", "kim"]
let reversed: [String] = names.sorted(by: backwards)
print(reversed)](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-8-320.jpg)
![CLOSURE
let reversed: [String]
reversed = names.sorted (by: { (left: String, right:
String) -> Bool in
return left > right })
print(reversed)
// ["yagom", "kim", "hana", "eric"]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-9-320.jpg)
![CLOSURE
//
let reversed: [String] = names.sorted() { (left: String,
right: String) -> Bool in
return left > right
}
// sorted(by:) .
let reversed: [String] = names.sorted { (left: String,
right: String) -> Bool in
return left > right
}](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-10-320.jpg)
![CLOSURE
// .
let reversed: [String] = names.sorted { (left, right) in
return left > right
}](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-11-320.jpg)
![CLOSURE
//
let reversed: [String] = names.sorted {
return $0 > $1
}
//
let reversed: [String] = names.sorted { $0 > $1 }](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-12-320.jpg)
![TRANSFORM USING
FOR STATEMENT
let numbers: [Int] = [0, 1, 2, 3, 4]
var doubledNumbers: [Int] = [Int]()
var strings: [String] = [String]()
// for
for number in numbers {
doubledNumbers.append(number * 2)
strings.append("(number)")
}
print(doubledNumbers) // [0, 2, 4, 6, 8]
print(strings) // ["0", "1", "2", "3", "4"]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-15-320.jpg)
![MAP EXAMPLE
// map
doubledNumbers = numbers.map({ (number: Int) -> Int in
return number * 2
})
strings = numbers.map({ (number: Int) -> String in
return "(number)"
})
print(doubledNumbers) // [0, 2, 4, 6, 8]
print(strings) // ["0", "1", "2", "3", "4"]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-16-320.jpg)
![MAP EXAMPLE
// , , (return)
//
doubledNumbers = numbers.map { $0 * 2 }
print(doubledNumbers) // [0, 2, 4, 6, 8]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-17-320.jpg)
![FILTER USING
FOR STATEMENT
let numbers: [Int] = [0, 1, 2, 3, 4, 5]
var evenNumbers: [Int] = [Int]()
// for
for number in numbers {
if number % 2 != 0 { continue }
evenNumbers.append(number)
}
print(evenNumbers) // [0, 2, 4]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-19-320.jpg)
![FILTER EXAMPLE
let numbers: [Int] = [0, 1, 2, 3, 4, 5]
let evenNumbers: [Int] = numbers.filter { (number: Int)
-> Bool in
return number % 2 == 0
}
print(evenNumbers) // [0, 2, 4]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-20-320.jpg)
![FILTER EXAMPLE
let oddNumbers: [Int] = numbers.filter {
$0 % 2 != 0
}
print(oddNumbers) // [1, 3, 5]](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-21-320.jpg)
![REDUCE USING
FOR STATEMENT
let numbers: [Int] = [2, 8, 15]
var sum: Int = 0
for number in numbers {
sum += number
}
print(sum) // 25](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-23-320.jpg)
![REDUCE EXAMPLE
let numbers: [Int] = [2, 8, 15]
// 0 .
let sum: Int = numbers.reduce(0, { (first: Int, second:
Int) -> Int in
print("(first) + (second)")
return first + second
})
print(sum) // 25
!](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-24-320.jpg)
![REDUCE EXAMPLE
let numbers: [Int] = [2, 8, 15]
// 0 .
let subtract: Int = numbers.reduce(0, { (first: Int,
second: Int) -> Int in
print("(first) - (second)")
return first - second
})
print(subtract) // -25](https://image.slidesharecdn.com/closurehigerorderfunctions-170325021318/85/Closure-Higher-order-function-in-Swift-25-320.jpg)
Closure, Higher-order function in Swift
- 1. CLOSURE & HIGHER-ORDER FUNCTION let us: Go! 2017 Spring
- 2. • Closure • Higher-Order Functions in Swift
- 3. CLOSURE
- 4. CLOSURE • • • , , , • :
- 6. CLOSURE
- 7. CLOSURE AS PARAMETER func sorted(by areInIncreasingOrder: (E, E) -> Bool) -> [E] (Type, Type) -> Type
- 8. CLOSURE func backwards(left: String, right: String) -> Bool { print("(left) (right) ") return left > right } let names: [String] = ["hana", "eric", "yagom", "kim"] let reversed: [String] = names.sorted(by: backwards) print(reversed)
- 9. CLOSURE let reversed: [String] reversed = names.sorted (by: { (left: String, right: String) -> Bool in return left > right }) print(reversed) // ["yagom", "kim", "hana", "eric"]
- 10. CLOSURE // let reversed: [String] = names.sorted() { (left: String, right: String) -> Bool in return left > right } // sorted(by:) . let reversed: [String] = names.sorted { (left: String, right: String) -> Bool in return left > right }
- 11. CLOSURE // . let reversed: [String] = names.sorted { (left, right) in return left > right }
- 12. CLOSURE // let reversed: [String] = names.sorted { return $0 > $1 } // let reversed: [String] = names.sorted { $0 > $1 }
- 13. HIGHER-ORDER FUNCTIONS • • map, filter, reduce
- 15. TRANSFORM USING FOR STATEMENT let numbers: [Int] = [0, 1, 2, 3, 4] var doubledNumbers: [Int] = [Int]() var strings: [String] = [String]() // for for number in numbers { doubledNumbers.append(number * 2) strings.append("(number)") } print(doubledNumbers) // [0, 2, 4, 6, 8] print(strings) // ["0", "1", "2", "3", "4"]
- 16. MAP EXAMPLE // map doubledNumbers = numbers.map({ (number: Int) -> Int in return number * 2 }) strings = numbers.map({ (number: Int) -> String in return "(number)" }) print(doubledNumbers) // [0, 2, 4, 6, 8] print(strings) // ["0", "1", "2", "3", "4"]
- 17. MAP EXAMPLE // , , (return) // doubledNumbers = numbers.map { $0 * 2 } print(doubledNumbers) // [0, 2, 4, 6, 8]
- 18. FILTER •
- 19. FILTER USING FOR STATEMENT let numbers: [Int] = [0, 1, 2, 3, 4, 5] var evenNumbers: [Int] = [Int]() // for for number in numbers { if number % 2 != 0 { continue } evenNumbers.append(number) } print(evenNumbers) // [0, 2, 4]
- 20. FILTER EXAMPLE let numbers: [Int] = [0, 1, 2, 3, 4, 5] let evenNumbers: [Int] = numbers.filter { (number: Int) -> Bool in return number % 2 == 0 } print(evenNumbers) // [0, 2, 4]
- 21. FILTER EXAMPLE let oddNumbers: [Int] = numbers.filter { $0 % 2 != 0 } print(oddNumbers) // [1, 3, 5]
- 22. REDUCE •
- 23. REDUCE USING FOR STATEMENT let numbers: [Int] = [2, 8, 15] var sum: Int = 0 for number in numbers { sum += number } print(sum) // 25
- 24. REDUCE EXAMPLE let numbers: [Int] = [2, 8, 15] // 0 . let sum: Int = numbers.reduce(0, { (first: Int, second: Int) -> Int in print("(first) + (second)") return first + second }) print(sum) // 25 !
- 25. REDUCE EXAMPLE let numbers: [Int] = [2, 8, 15] // 0 . let subtract: Int = numbers.reduce(0, { (first: Int, second: Int) -> Int in print("(first) - (second)") return first - second }) print(subtract) // -25
- 26. REDUCE EXAMPLE // 3 . let sumFromThree = numbers.reduce(3) { $0 + $1 } print(sumFromThree) // 28 /* var sum: Int = 3 for number in numbers { sum += number } */
- 27. Q&A