一、contains

返回一个布尔值，指示序列的每个元素是否满足给定的条件。如果有一个满足即返回。


let expenses = [21.37, 55.21, 9.32, 10.18, 388.77, 11.41]let hasBigPurchase = expenses.contains { $0 > 100 }// 'hasBigPurchase' == true

Sequence协议源码


@inlinablepublic func contains(_ element: Element) -> Bool {if let result = _customContainsEquatableElement(element) {return result} else {return self.contains { $0 == element }}}


@inlinablepublic func contains(where predicate: (Element) throws -> Bool) rethrows -> Bool {for e in self {if try predicate(e) {return true}}return false}

二、allSatisfy

返回一个布尔值，指示序列的每个元素是否满足给定的条件。需要所有元素都满足。


let names = ["Sofia", "Camilla", "Martina", "Mateo", "Nicolás"]let allHaveAtLeastFive = names.allSatisfy({ $0.count >= 5 })// allHaveAtLeastFive == true

Sequence协议源码
allSatisfy里面调用了contains方法


@inlinablepublic func allSatisfy(_ predicate: (Element) throws -> Bool) rethrows -> Bool {return try !contains { try !predicate($0) }}

三、reversed

返回一个数组，该数组以相反的顺序包含此序列的元素。


let list = [1, 2, 3, 4, 5]
let ret = list.reversed()
print(Array(ret))
---console
[5, 4, 3, 2, 1]

Sequence协议源码


@inlinablepublic __consuming func reversed() -> [Element] {// FIXME(performance): optimize to 1 pass?  But Array(self) can be// optimized to a memcpy() sometimes.  Those cases are usually collections,// though.var result = Array(self)let count = result.countfor i in 0..<count/2 {result.swapAt(i, count - ((i + 1) as Int))}return result}

四、lexicographicallyPrecedes

返回一个布尔值，该值指示在字典顺序(字典)中该序列是否在另一个序列之前，使用给定条件语句比较元素。


let list = [1, 2, 3, 4, 5]
let list2 = [2, 2, 3, 5]
let ret1 = list.lexicographicallyPrecedes(list2)
let ret2 = list2.lexicographicallyPrecedes(list)
print(ret1, ret2)
---console
true false

Sequence协议源码


@inlinablepublic func lexicographicallyPrecedes<OtherSequence: Sequence>(_ other: OtherSequence) -> Bool where OtherSequence.Element == Element {return self.lexicographicallyPrecedes(other, by: <)}


@inlinablepublic func lexicographicallyPrecedes<OtherSequence: Sequence>(_ other: OtherSequence,by areInIncreasingOrder: (Element, Element) throws -> Bool) rethrows -> Bool where OtherSequence.Element == Element {var iter1 = self.makeIterator()var iter2 = other.makeIterator()while true {if let e1 = iter1.next() {if let e2 = iter2.next() {if try areInIncreasingOrder(e1, e2) {return true}if try areInIncreasingOrder(e2, e1) {return false}continue // Equivalent}return false}return iter2.next() != nil}}