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  • Swift的74个常用内置函数

    发布:达内南京IOS培训      来源:达内新闻      

  • 南京iOS培训专家介绍一下Swift的74个常用内置函数,内置函数是指无需引入任何模块即可以直接使用的函数,非常实用,值得大家参考。

    //断言,参数如果为`true`则继续,否则抛出异常
    //assert mentioned on page 55
    assert(true)
    //计算序列的元素个数
    // countElements mentioned on page 79
    countElements("foo") == 3
    //返回一个新的序列,其中每个元素是一个元组,
    //第一个值为原来元素所在的位置`index`,第二个为原来序列中的元素
    // enumerate mentioned on page 94
    for (i, j) in enumerate(["A", "B"]) {
     // "0:A", "1:B" will be printed
    println("\(i):\(j)")
    }
    //返回所有参数中的最小值
    // min mentioned on page 246
    min(8, 2, 3) == 2
    //打印
    // print mentioned on page 85
    print("Hello ")
    //打印(带换行)
    // 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)
    }
    abs(signedNumber):返回数字的绝对值
    abs(-1) == 1
    abs(-42) == 42
    abs(42) == 42
    contains(sequence, element):如果某个序列sequence(比如说一个数组)包含指定的元素element,则返回true,否则返回false。
    var languages = ["Swift", "Objective-C"]
    contains(languages, "Swift") == true
    contains(languages, "Java") == false
    contains([29, 85, 42, 96, 75], 42) == true
    dropFirst(sequence):返回一个去掉了首个元素的、新的序列(比如一个新数组)。
    var languages = ["Swift", "Objective-C"]
    var oldLanguages = dropFirst(languages)
    equal(oldLanguages, ["Objective-C"]) == true
    dropLast(sequence):返回一个去掉了最后一个元素的、新的序列(比如一个新数组)。
    var languages = ["Swift", "Objective-C"]
    var newLanguages = dropLast(languages)
    equal(newLanguages, ["Swift"]) == true
    dump(object):打印出某个对象object的所有信息
    var languages = ["Swift", "Objective-C"]
    dump(languages)
    // Prints:
    // ▿ 2 elements
    // - [0]: Swift
    // - [1]: Objective-C
    equal(sequence1, sequence2):判断两个序列是否相等
    var languages = ["Swift", "Objective-C"]
    equal(languages, ["Swift", "Objective-C"]) == true
    var oldLanguages = dropFirst(languages)
    equal(oldLanguages, ["Objective-C"]) == true

    filter(sequence, includeElementClosure):对序列sequence中每个元素都执行includeElementClosure闭包,并将所有闭包结果为true的元素合成一个新序列sequence并返回。

    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,则返回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的复数)
    equal(indices([29, 85, 42]), [0, 1, 2])
    for i in indices([29, 85, 42]) {
     // 0, 1, 2
     println(i)
    }
    join(separator, sequence):将序列sequence通过分隔符separator连成一个字符串,并返回此字符串
    join(":", ["A", "B", "C"]) == "A:B:C"
    var languages = ["Swift", "Objective-C"]
    join("/", languages) == "Swift/Objective-C"

    map(sequence, transformClosure):对序列sequence中每个元素都执行includeElementClosure闭包,并将所有闭包的结果合成一个新序列sequence并返回。

    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.):返回参数中的最大值。
    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):给定一个序列sequence,以及一个初始值initial,然后将initial和序列里的第1个元素作为参数传入combineClosure中进行运算,得到的结果保存到initial;然后再将initial和第2个元素传入combineClosure中计算,结果保存到initial;重复计算直到所有sequence中的元素都计算完毕,并返回最终的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中开头的元素跟序列sequence2中的所有元素都相等,则返回true,否则返回false。

    startsWith("foobar", "foo") == true
    startsWith(10..100, 10..15) == true
    var languages = ["Swift", "Objective-C"]
    startsWith(languages, ["Swift"]) == true

    以上这些函数是达内IOS培训专家整理的,在Swift编程中会经常用到的函数。

    完整74个内置函数:

    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(...)
    umericCast(...)
    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(...)

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