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
@inlinable
public func contains(_ element: Element) -> Bool {
if let result = _customContainsEquatableElement(element) {
return result
} else {
return self.contains { $0 == element }
}
}
@inlinable
public 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
@inlinable
public 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
@inlinable
public __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.count
for 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
@inlinable
public func lexicographicallyPrecedes<OtherSequence: Sequence>(
_ other: OtherSequence
) -> Bool where OtherSequence.Element == Element {
return self.lexicographicallyPrecedes(other, by: <)
}
@inlinable
public 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
}
}
