Closure, Higher-order function in Swift

CLOSURE 
& 
HIGHER-ORDER FUNCTION
let us: Go! 
2017 Spring

• Closure
• Higher-Order Functions in Swift

CLOSURE
•
•
• , , ,
• :

CLOSURE
• ,
• return
•
•

CLOSURE AS PARAMETER
func sorted(by areInIncreasingOrder: (E, E) -> Bool) -> [E]
 
(Type, Type) -> Type

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)

CLOSURE
let reversed: [String]
reversed = names.sorted (by: { (left: String, right:
String) -> Bool in
return left > right })
print(reversed)
// ["yagom", "kim", "hana", "eric"]

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
}

CLOSURE
// .
let reversed: [String] = names.sorted { (left, right) in
return left > right
}

CLOSURE
//
let reversed: [String] = names.sorted {
return $0 > $1
}
//
let reversed: [String] = names.sorted { $0 > $1 }

HIGHER-ORDER FUNCTIONS
•
• map, ﬁlter, reduce

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"]

MAP EXAMPLE
// map
doubledNumbers = numbers.map({ (number: Int) -> Int in
return number * 2
})
 
strings = numbers.map({ (number: Int) -> String in  
return "(number)"
})
print(strings) // ["0", "1", "2", "3", "4"]

MAP EXAMPLE
// , , (return)
//
doubledNumbers = numbers.map { $0 * 2 }

FILTER USING  
FOR STATEMENT
let numbers: [Int] = [0, 1, 2, 3, 4, 5]
var evenNumbers: [Int] = [Int]()
// for
if number % 2 != 0 { continue }
evenNumbers.append(number)
}
print(evenNumbers) // [0, 2, 4]

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]

FILTER EXAMPLE
let oddNumbers: [Int] = numbers.filter {
$0 % 2 != 0
}
print(oddNumbers) // [1, 3, 5]

REDUCE USING
FOR STATEMENT
let numbers: [Int] = [2, 8, 15]
var sum: Int = 0
sum += number
}
print(sum) // 25

REDUCE EXAMPLE
// 0 .
let sum: Int = numbers.reduce(0, { (first: Int, second:
Int) -> Int in
print("(first) + (second)")
return first + second
})
print(sum) // 25
!

REDUCE EXAMPLE
// 0 .
let subtract: Int = numbers.reduce(0, { (first: Int,
second: Int) -> Int in
print("(first) - (second)")
return first - second
})
print(subtract) // -25

REDUCE EXAMPLE
// 3 .
let sumFromThree = numbers.reduce(3) { $0 + $1 }
print(sumFromThree)
// 28 
 
 
/*
var sum: Int = 3
sum += number
}
*/

Closure, Higher-order function in Swift

More Related Content

What's hot

Similar to Closure, Higher-order function in Swift

Recently uploaded

Closure, Higher-order function in Swift