簡(jiǎn)介:
Swift發(fā)布后提供了很多高效的標(biāo)準(zhǔn)庫(kù)函數(shù),其實(shí)早在 Swift 正式發(fā)布之前沛善，iOS / Cocoa 開(kāi)發(fā)者都可以使用諸如 ObjectiveSugar 或者 ReactiveCocoa 第三方庫(kù)金刁，實(shí)現(xiàn)類似 map、flatMap 或 filter 等函數(shù)式編程的構(gòu)建媳友。
并且通過(guò)使用函數(shù)式編程能夠更好地表達(dá)你的意圖醇锚，減少代碼的行數(shù)焊唬，以及使用鏈?zhǔn)浇Y(jié)構(gòu)構(gòu)建復(fù)雜的邏輯看靠，更顯清爽。
接下來(lái),介紹一下常用的一些標(biāo)準(zhǔn)庫(kù)函數(shù):
1.在文檔中提到的庫(kù)函數(shù)(The Swift Programming Language)
//斷言芳杏，參數(shù)如果為true則繼續(xù)爵赵，否則拋出異常
assert(true)
//swift 1.0 計(jì)算序列的元素個(gè)數(shù)
let str = "sk87v5"
countElements("str") == 6
//swift2.0后計(jì)算字符串長(zhǎng)度
print(str.characters.count)//6
//swift2.0后計(jì)算數(shù)組元素
let arr = ["sk", "wyj", "jj"]
print(arr.count)//3
//返回一個(gè)新的序列空幻，其中每個(gè)元素是一個(gè)元組秕铛，第一個(gè)值為原來(lái)元素所在的位置index但两，第二個(gè)為原來(lái)序列中的元素
let array = ["N", "B","A"]
for (i, j) in array.enumerate() {
print("\(i):\(j)")
}
打印結(jié)果:
//0:N
//1:B
//2:A
//返回所有參數(shù)中的最小值
min(9, 2, 4) == 2
//打印
print("Hello")
//Swift1.0 使用的打印 （帶換行)
// println mentioned on page 4
println("World")
//排序
// sort mentioned on page 14
let array = ["N", "B","A"]
for i in array.sort() {
print(i) // A B N
}
2.文檔未提的實(shí)用函數(shù)
- Swift 1.0
- map(sequence, transformClosure)：對(duì)數(shù)組中每個(gè)元素都執(zhí)行閉包谨湘，并將所有閉包的結(jié)果合成一個(gè)新數(shù)組并返回紧阔。
- Swift 2.0
- map(transform: (Int) throws -> T):對(duì)數(shù)組中每個(gè)元素都執(zhí)行閉包中的操作擅耽，并將所有閉包的結(jié)果合成一個(gè)新序列數(shù)組并返回。
//swift 2.0
let array = [1, 10, 22, 40, 88, 90, 99]
//1.常規(guī)用法
let newArr = array.map { (a : Int) -> Int in
return a + 10
}
print(newArr)
//2.簡(jiǎn)化用法
let newArr = array.map({$0 + 10})
print(newArr)
//打印結(jié)果:
[11, 20, 32, 50, 98, 100, 109]
- (Swift 1.0)
- filter(sequence, includeElementClosure)：
- (Swift 2.0)
- filter(includeElement: (Int) throws -> Bool)
對(duì)序列數(shù)組中每個(gè)元素都執(zhí)行includeElement閉包憾儒，并將所有閉包結(jié)果為true的元素合成一個(gè)新數(shù)組并返回起趾。
//swift 2.0
let array = [1, 10, 22, 40, 88, 90, 99]
//1.常規(guī)用法
let newArr = array.filter { (a : Int) -> Bool in
return a % 10 == 0
}
print(newArr)//[10, 40, 90]\n
//2.簡(jiǎn)化用法
let newArr = array.filter({$0 % 10 == 0})
print(newArr)//[10, 40, 90]\n
- Swift 1.0
- reduce(sequence, initial, combineClosure)：給定一個(gè)數(shù)組sequence，以及一個(gè)初始值initial冷蚂，然后將initial和數(shù)組里的第1個(gè)元素作為參數(shù)傳入combineClosure閉包中進(jìn)行運(yùn)算，得到的結(jié)果保存到initial艺骂；然后再將initial和第2個(gè)元素傳入combineClosure閉包中計(jì)算钳恕，結(jié)果保存到initial忧额；重復(fù)計(jì)算直到所有sequence中的元素都計(jì)算完畢睦番，并返回最終的initial值耍属。
- Swift 2.0
- reduce(initial: T, combine: (T, String) throws -> T)
//1.傳統(tǒng)求和
let arrNum = [1, 2, 3, 4 ,5]
var sum = 0
for num in arrNum {
sum = sum + num
}
print(sum) //15
//2.傳統(tǒng)求積
var a = 1
for num in arrNum {
a = a * num
}
print(a)//120
//2.reduce求和,求積:
let arrNum = [1, 2, 3, 4, 5]
//簡(jiǎn)化一:
let sum = arrNum.reduce(0, combine: {$0 + $1})
let a = arrNum.reduce(1, combine: {$0 * $1})
//簡(jiǎn)化二:
//初始值 initial 為 0，每次遍歷數(shù)組元素示启，執(zhí)行 + 操作
let sum = arrNum.reduce(0, combine: +)
//初始值 initial 為 1夫嗓，每次遍歷數(shù)組元素，執(zhí)行 * 操作
let a = arrNum.reduce(1, combine: *)
print(sum)
print(a)
let arr = ["sk", "wyj", "jj", "dyf", "zjz"]
let arrNew = arr.reduce("87v5", combine: + )
print(arrNew)
- abs(signedNumber)：返回?cái)?shù)字的絕對(duì)值
abs(-1) == 1 //true
abs(-42) == 42 //true
abs(42) == 42 //true
- contains(sequence, element)：
- 如果某個(gè)序列
sequence（比如說(shuō)一個(gè)數(shù)組）包含指定的元素element劳跃，則返回true，否則返回false刨仑。
let arr = ["sk", "wyj", "jj", "dyf", "zjz"]
arr.contains("sk")// true
arr.contains("87v5")// false
- dropFirst(sequence)：
- 返回一個(gè)去掉了首個(gè)元素的辙诞、新的序列（比如一個(gè)新數(shù)組）飞涂。
let array = ["xmg", "sk", "why"]
var arrayNew = array.dropFirst() //["sk", "why"]
//去掉前2個(gè)元素
var arrayNewTwo = array.dropFirst(2) //["why"]
//注:elementsEqual() iOS9.0后可用
arrayNew.elementsEqual(array) //false
- dropLast(sequence)：返回一個(gè)去掉了最后一個(gè)元素的祈搜、新的序列（比如一個(gè)新數(shù)組）。
let array = ["xmg", "sk", "why"]
var arrayNew = array.dropLast() //["xmg", "sk"]
//去掉后2個(gè)元素
var arrayNewTwo = array.dropLast(2) //["xmg"]
arrayNew.elementsEqual(["xmg", "sk"]) //true
- dump(object)：打印出某個(gè)對(duì)象object的所有信息
let array = ["xmg", "sk", "why"]
dump(array) //["xmg", "sk", "why"]
// Prints:
//3 elements
//- [0]: xmg
//- [1]: sk
//- [2]: why
//注:dump和print的區(qū)別:dump打印的是內(nèi)容,print打印的是內(nèi)容+ 換行符的字符串
print(array)//"["xmg", "sk", "why"]\n"
- elementsEqual()：判斷兩個(gè)序列是否相等
let array = ["xmg", "sk", "why"]
array.elementsEqual(["sk"]) //false
let arrayOne = array.dropLast()
let arrayTwo = ["xmg", "sk"]
arrayOne.elementsEqual(arrayTwo) //true
- (Swift1.0)
- find(sequence, element)：返回序列sequence中某元素element的位置index。如果序列中不存在此元素蘸秘，則返回nil醋虏。
- (Swift2.0)
- arr.indexOf(element: String):返回?cái)?shù)組中某元素element的位置index颈嚼。如果數(shù)組中不存在此元素粘舟，則返回nil
//find(sequence, element)
let arr = ["sk", "wyj", "jj"]
find(arr, "sk") == 0
find(arr, "dyf") == nil
find([29, 85, 42, 96, 75], 42) == 2
//indexOf(element: String)
let arr = ["sk", "wyj", "jj"]
let index = arr.indexOf("sk") //0
let index2 = arr.indexOf("dyf")//nil
- (Swift 1.0)
- indices(sequence)：返回序列sequence中所有元素的位置（indices是index的復(fù)數(shù)）
- (Swift 2.0)
- 改為屬性indices,返回Range類型
//swift1.0
equal(indices([29, 85, 42]), [0, 1, 2])
for i in indices([29, 85, 42]) {
// 0, 1, 2
print(i)
}
//swift2.0
let arr = ["sk", "wyj", "jj"]
let a = arr.indices
print(a) //0..<3
- (Swift1.0)
- join(separator, sequence)：將序列sequence通過(guò)分隔符separator連成一個(gè)字符串柑肴，并返回此字符串晰骑。
- (Swift2.0)
- joinWithSeparator(separator: String)
//swift1.0
join(":", ["A", "B", "C"]) == "A:B:C"
let arr = ["sk", "wyj", "jj"]
join("/", arr) == "sk/wyj/jj"
//swift2.0
let arr = ["sk", "wyj", "jj"]
let joinArr = arr.joinWithSeparator("/")
print(joinArr)
打印結(jié)果:
sk/wyj/jj
- max(comparable1, comparable2, etc.)：返回參數(shù)中的最大值。
max(0, 1) == 1
max(8, 2, 3) == 8
- maxElement(sequence)：返回序列sequence中的最大值骤公。
//swift 1.0
let array = [1, 10, 22, 40, 88, 90, 99]
maxElement(array) //99
//swift 2.0
let array = [1, 10, 22, 40, 88, 90, 99]
array.maxElement() //99
- minElements(sequence)：返回序列sequence中的最小值扬跋。
//swift 1.0
let array = [1, 10, 22, 40, 88, 90, 99]
minElement(array) //1
//swift 2.0
let array = [1, 10, 22, 40, 88, 90, 99]
array.minElement() //1
- reverse(sequence)：返回逆序的序列sequence。
let array = [1, 10, 22, 40, 88, 90, 99]
for i in array.reverse() {
print(i)
}
- Swift 1.0
- startsWith(sequence1, sequence2)：如果序列sequence1中開(kāi)頭的元素跟序列sequence2中的所有元素都相等洒试，則返回true，否則返回false痪宰。
- Swift 2.0
- startsWith(other: SequenceType)
//swift 1.0
startsWith(1..20, 1..5) == true
let arr1 = ["sk", "wyj", "jj"]
let arr2 = ["sk"]
startsWith(arr1, arr2) == true
//swift 2.0
let range1 = 1..<20
let range2 = 1..<5
if range1.startsWith(range2) {
print("range2所有元素和range1開(kāi)頭元素相等")
}else {
print("不相等")
}
let arr1 = ["sk", "wyj", "jj"]
let arr2 = ["sk"]
if arr1.startsWith(arr2) {
print("arr2所有元素和arr1開(kāi)頭所有元素相等")
}else {
print("不相等")
}
附:Swift1.0 中74個(gè)內(nèi)置函數(shù)：
abs(...)
advance(...)
alignof(...)
alignofValue(...)
assert(...)
bridgeFromObjectiveC(...)
bridgeFromObjectiveCUnconditional(...)
bridgeToObjectiveC(...)
bridgeToObjectiveCUnconditional(...)
c_malloc_size(...)
c_memcpy(...)
c_putchar(...)
contains(...)
count(...)
countElements(...)
countLeadingZeros(...)
debugPrint(...)
debugPrintln(...)
distance(...)
dropFirst(...)
dropLast(...)
dump(...)
encodeBitsAsWords(...)
enumerate(...)
equal(...)
filter(...)
find(...)
getBridgedObjectiveCType(...)
getVaList(...)
indices(...)
insertionSort(...)
isBridgedToObjectiveC(...)
isBridgedVerbatimToObjectiveC(...)
isUniquelyReferenced(...)
join(...)
lexicographicalCompare(...)
map(...)
max(...)
maxElement(...)
min(...)
minElement(...)
numericCast(...)
partition(...)
posix_read(...)
posix_write(...)
print(...)
println(...)
quickSort(...)
reduce(...)
reflect(...)
reinterpretCast(...)
reverse(...)
roundUpToAlignment(...)
sizeof(...)
sizeofValue(...)
sort(...)
split(...)
startsWith(...)
strideof(...)
strideofValue(...)
swap(...)
swift_MagicMirrorData_summaryImpl(...)
swift_bufferAllocate(...)
swift_keepAlive(...)
toString(...)
transcode(...)
underestimateCount(...)
unsafeReflect(...)
withExtendedLifetime(...)
withObjectAtPlusZero(...)
withUnsafePointer(...)
withUnsafePointerToObject(...)
withUnsafePointers(...)
withVaList(...)
codeStraight原創(chuàng)文章,如有錯(cuò)誤,歡迎指正!
http://www.reibang.com/p/2c7407c76ad8
