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blog.csdn.net/hello_hwc
前言：和OC不同，Swift有很多全局的函数，这些全局函数对简化代码来说很有用，目前Swift出到了2.0,不过我这篇文章还是用Swift1.2写的示例代码。
Count－统计数量
文档
func count<T : _CollectionType>(x: T) -> T.Index.distance
Description
Return the number of elements in x.
O(1) if T.Index is RandomAccessIndexType; O(N) otherwise.
示例
let arr = [1,2,3,4]
let dic = [1:2,"a":"b"]
let str = "Wenchenhuang"
println(count(arr))//4
println(count(dic))//2
println(count(str))//12
Filter－条件过滤
文档
func filter<S : SequenceType>(source: S,includeElement: (S.Generator.Element) -> Bool) -> [S.Generator.Element]
Description
Return an Array containing the elements of source,in order,that satisfy the predicate includeElement.
示例－过滤长度大于4的字符串
let array = ["Wen","Chen","Huang"]
let filteredArray = filter(array,{ (element:String) -> Bool in return count(element)>4; }) println(filteredArray)
也可以简化
let filteredArray = filter(array) {count($0)>4}
Map - 映射集合类型，返回数组
文档
func map<C : CollectionType,T>(source: C,transform: (C.Generator.Element) -> T) -> [T]
Description
Return an Array containing the results of mapping transform over source.
示例
let array = ["Wen","Huang"]
let mapedaray = map(array,{ (element:String) -> Int in return count(element) }) println(mapedaray) //［3，4，5］
同样可以简化
let mapedaray = map(array){count($0)}
Reduce - 把数组结合到一起
文档
func reduce<S : SequenceType,U>(sequence: S,initial: U,combine: @noescape (U,S.Generator.Element) -> U) -U
Description
Return the result of repeatedly calling combine with an accumulated value initialized to initial and each element of `sequence`,in turn.
示例
let array = ["Wen","Huang"]
let reduceResult = reduce(array,"Hello ") { (originValue:String,element:String) -> String in
return originValue + element;
}
println(reduceResult) //Hello WenChenHuang
可以简化
let reduceResult = reduce(array,"Hello ") { $0 + $1}
进一步简化
let reduceResult = reduce(array,"Hello ",+)