只有拆分才是正确的答案，这里有两个以上空格的差异。

雨燕5

var temp = "Hello world     ni hao"
let arr  = temp.components(separatedBy: .whitespacesAndNewlines)
// ["Hello", "world", "", "", "", "", "ni", "hao"]
let arr2 = temp.components(separatedBy: " ")
// ["Hello", "world", "", "", "", "", "ni", "hao"]
let arr3 = temp.split(whereSeparator: {$0 == " "})
// ["Hello", "world", "ni", "hao"]

空白问题

一般来说，人们会一次又一次地重复这个问题和糟糕的解决方案。这是一个空间吗？“”以及“\n”、“\t”或一些您从未见过的unicode空白字符，在很大程度上是不可见的。虽然你可以逃脱

弱解决方案

import Foundation
let pieces = "Mary had little lamb".componentsSeparatedByString(" ")

如果你需要在现实中动摇你的控制，请观看WWDC视频中的字符串或日期。简而言之，让苹果解决这类平凡的任务几乎总是更好的。

稳健的解决方案：使用NSCharacterSet

IMHO，正确做到这一点的方法是使用NSCharacterSet，因为正如前面所述，您的空白可能不是您所期望的，并且Apple提供了一个空白字符集。要探索提供的各种字符集，请查看Apple的NSCharacterSet开发人员文档，然后，如果不符合您的需要，才可以扩充或构建新的字符集。

NSCharacterSet空白

返回包含Unicode常规中的字符的字符集Z类和字符表（U+0009）。

let longerString: String = "This is a test of the character set splitting system"
let components = longerString.components(separatedBy: .whitespaces)
print(components)

Swift的方法是使用全局拆分函数，如下所示：

var fullName = "First Last"
var fullNameArr = split(fullName) {$0 == " "}
var firstName: String = fullNameArr[0]
var lastName: String? = fullNameArr.count > 1 ? fullNameArr[1] : nil

使用Swift 2

在Swift 2中，由于引入了内部CharacterView类型，拆分的使用变得有点复杂。这意味着String不再采用SequenceType或CollectionType协议，您必须改为使用.characts属性来访问String实例的CharacterView类型表示。（注意：CharacterView确实采用SequenceType和CollectionType协议）。

let fullName = "First Last"
let fullNameArr = fullName.characters.split{$0 == " "}.map(String.init)
// or simply:
// let fullNameArr = fullName.characters.split{" "}.map(String.init)

fullNameArr[0] // First
fullNameArr[1] // Last 

Swift 4使拆分字符变得更加容易，只需为字符串使用新的拆分函数即可。

例子：让s=“嗨，你好”让a=s.split（分隔符：“，”）打印（a）

现在您得到了一个带有“hi”和“hello”的数组。

将字符串拆分为数组的简单方法

var fullName:String=“First Last”；var fullNameArr=fullName.componentsSeparatedByString（“”）var firstName:String=fullNameArr[0]var lastName:String=fullNameArr[1]

非顶部：

对于搜索如何使用子字符串（而不是字符）拆分字符串的人来说，下面是一个有效的解决方案：

// TESTING
let str1 = "Hello user! What user's details? Here user rounded with space."
let a = str1.split(withSubstring: "user") // <-------------- HERE IS A SPLIT
print(a) // ["Hello ", "! What ", "\'s details? Here ", " rounded with space."]

// testing the result
var result = ""
for item in a {
    if !result.isEmpty {
        result += "user"
    }
    result += item
}
print(str1) // "Hello user! What user's details? Here user rounded with space."
print(result) // "Hello user! What user's details? Here user rounded with space."
print(result == str1) // true

/// Extension providing `split` and `substring` methods.
extension String {
    
    /// Split given string with substring into array
    /// - Parameters:
    ///   - string: the string
    ///   - substring: the substring to search
    /// - Returns: array of components
    func split(withSubstring substring: String) -> [String] {
        var a = [String]()
        var str = self
        while let range = str.range(of: substring) {
            let i = str.distance(from: str.startIndex, to: range.lowerBound)
            let j = str.distance(from: str.startIndex, to: range.upperBound)
            let left = str.substring(index: 0, length: i)
            let right = str.substring(index: j, length: str.length - j)
            a.append(left)
            str = right
        }
        if !str.isEmpty {
            a.append(str)
        }
        return a
    }
    
    /// the length of the string
    public var length: Int {
        return self.count
    }
    
    /// Get substring, e.g. "ABCDE".substring(index: 2, length: 3) -> "CDE"
    ///
    /// - parameter index:  the start index
    /// - parameter length: the length of the substring
    ///
    /// - returns: the substring
    public func substring(index: Int, length: Int) -> String {
        if self.length <= index {
            return ""
        }
        let leftIndex = self.index(self.startIndex, offsetBy: index)
        if self.length <= index + length {
            return String(self[leftIndex..<self.endIndex])
        }
        let rightIndex = self.index(self.endIndex, offsetBy: -(self.length - index - length))
        return String(self[leftIndex..<rightIndex])
    }

}