本文譯自 Swift Standard Library: Documented and undocumented built-in functions in the Swift standard library – the complete list with all 74 functions。我不是原作者,我只是勤勞的翻譯工:)文中作者沒有提及他是如何發現這麼多未在文檔中體現的內置函數的,估計是反編譯的結果。我測試了好多個都能用,而且Xcode還會給出語法提示:)
Swift包含了74個內置函數,但在The
Swift Programming Langage
一書中只介紹了其中的7個,其它的都沒有在文檔中體現。
這篇文章列舉出了所有的Swift庫函數。文中所謂的庫函數
是指無需引入任何模塊(比如說Fundation等)即可以直接使用的函數。
下面先來看看7個在文檔中提到的庫函數:
//斷言,參數如果爲`true`則繼續,否則拋出異常
// assert mentioned on page 55
assert(true)
//計算序列的元素個數
// countElements mentioned on page 79
countElements("foo") == 3
//返回一個新的序列,其中每個元素是一個元組,第一個值爲原來元素所在的位置`index`,第二個爲原來序列中的元素
// enumerate mentioned on page 94
for (i, j) in enumerate(["A", "B"]) {
// "0:A", "1:B" will be printed
println("\(i):\(j)")
}
//返回所有參數中的最小值
// min mentioned on page 246
min(8, 2, 3) == 2
//打印
// print mentioned on page 85
print("Hello ")
//打印(帶換行)
// println mentioned on page 4
println("World")
//排序
// sort mentioned on page 14
for i in sort(["B", "A"]) {
// "A", "B" will be printed
println(i)
}
下面列出一些很實用,但未在文檔中體現的庫函數:
abs(signedNumber)
:返回數字的絕對值
abs(-1) == 1
abs(-42) == 42
abs(42) == 42
contains(sequence,
element)
:如果某個序列sequence
(比如說一個數組)包含指定的元素element
,則返回true
,否則返回false
。
var languages = ["Swift", "Objective-C"]
contains(languages, "Swift") == true
contains(languages, "Java") == false
contains([29, 85, 42, 96, 75], 42) == true
dropFirst(sequence)
:返回一個去掉了首個元素的、新的序列(比如一個新數組)。
var languages = ["Swift", "Objective-C"]
var oldLanguages = dropFirst(languages)
equal(oldLanguages, ["Objective-C"]) == true
dropLast(sequence)
:返回一個去掉了最後一個元素的、新的序列(比如一個新數組)。
var languages = ["Swift", "Objective-C"]
var newLanguages = dropLast(languages)
equal(newLanguages, ["Swift"]) == true
dump(object)
:打印出某個對象object
的所有信息
var languages = ["Swift", "Objective-C"]
dump(languages)
// Prints:
// ▿ 2 elements
// - [0]: Swift
// - [1]: Objective-C
equal(sequence1,
sequence2)
:判斷兩個序列是否相等
var languages = ["Swift", "Objective-C"]
equal(languages, ["Swift", "Objective-C"]) == true
var oldLanguages = dropFirst(languages)
equal(oldLanguages, ["Objective-C"]) == true
filter(sequence,
includeElementClosure)
:對序列sequence
中每個元素都執行includeElementClosure
閉包,並將所有閉包結果爲true
的元素合成一個新序列sequence
並返回。
for i in filter(1...100, { $0 % 10 == 0 }) {
// 10, 20, 30, ...
println(i)
assert(contains([10, 20, 30, 40, 50, 60, 70, 80, 90, 100], i))
}
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,則返回nil
。
var languages = ["Swift", "Objective-C"]
find(languages, "Objective-C") == 1
find(languages, "Java") == nil
find([29, 85, 42, 96, 75], 42) == 2
indices(sequence)
:返回序列sequence
中所有元素的位置(indices是index的複數)
equal(indices([29, 85, 42]), [0, 1, 2])
for i in indices([29, 85, 42]) {
// 0, 1, 2
println(i)
}
join(separator,
sequence)
:將序列sequence
通過分隔符separator
連成一個字符串,並返回此字符串。
join(":", ["A", "B", "C"]) == "A:B:C"
var languages = ["Swift", "Objective-C"]
join("/", languages) == "Swift/Objective-C"
map(sequence,
transformClosure)
:對序列sequence
中每個元素都執行includeElementClosure
閉包,並將所有閉包的結果合成一個新序列sequence
並返回。
equal(map(1...3, { $0 * 5 }), [5, 10, 15])
for i in map(1...10, { $0 * 10 }) {
// 10, 20, 30, ...
println(i)
assert(contains([10, 20, 30, 40, 50, 60, 70, 80, 90, 100], i))
}
max(comparable1,
comparable2, etc.)
:返回參數中的最大值。
max(0, 1) == 1
max(8, 2, 3) == 8
maxElement(sequence)
:返回序列sequence
中的最大值。
maxElement(1...10) == 10
var languages = ["Swift", "Objective-C"]
maxElement(languages) == "Swift"
minElements(sequence)
:返回序列sequence
中的最小值。
minElement(1...10) == 1
var languages = ["Swift", "Objective-C"]
minElement(languages) == "Objective-C"
reduce(sequence,
initial, combineClosure)
:給定一個序列sequence
,以及一個初始值initial
,然後將initial
和序列裏的第1個元素作爲參數傳入combineClosure
中進行運算,得到的結果保存到initial
;然後再將initial
和第2個元素傳入combineClosure
中計算,結果保存到initial
;重複計算直到所有sequence
中的元素都計算完畢,並返回最終的initial
值。
var languages = ["Swift", "Objective-C"]
reduce(languages, "", { $0 + $1 }) == "SwiftObjective-C"
reduce([10, 20, 5], 1, { $0 * $1 }) == 1000
reverse(sequence)
:返回逆序的序列sequence
。
equal(reverse([1, 2, 3]), [3, 2, 1])
for i in reverse([1, 2, 3]) {
// 3, 2, 1
println(i)
}
startsWith(sequence1,
sequence2)
:如果序列sequence1
中開頭的元素跟序列sequence2
中的所有元素都相等,則返回true
,否則返回false
。
startsWith("foobar", "foo") == true
startsWith(10..100, 10..15) == true
var languages = ["Swift", "Objective-C"]
startsWith(languages, ["Swift"]) == true
上面提到的函數是我認爲在Swift編程中會經常用到的函數。下面將列出完整的74個函數列表。
完整74個內置函數:
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(...)