var fullName = "James Keagan Michael"
let first = fullName.components(separatedBy: " ").first?.isEmpty == false ? fullName.components(separatedBy: " ").first! : "John"
let last =  fullName.components(separatedBy: " ").last?.isEmpty == false && fullName.components(separatedBy: " ").last != fullName.components(separatedBy: " ").first ? fullName.components(separatedBy: " ").last! : "Doe"

不允许使用相同的名字和姓氏如果全名无效，则取占位符值“John Doe”

最简单的解决方案是

let fullName = "First Last"

let components = fullName.components(separatedBy: .whitespacesAndNewlines).compactMap { $0.isEmpty ? nil : $0 }

这将处理不同类型的一行中的多个空格（空格、制表符、换行符等），并且只返回一个两元素数组，您可以更改CharacterSet以包含更多您喜欢的字符，如果您想获得切割符，可以使用正则表达式解码器，这允许您编写正则表达式，该表达式可用于将字符串直接解码到实现解码协议的自己的类/结构中。对于像这样的东西来说，这是过度的，但如果您将其用作更复杂字符串的示例，则可能更有意义。

let str = "one two"
let strSplit = str.characters.split(" ").map(String.init) // returns ["one", "two"]

Xcode 7.2（7C68）

在Swift 4.2和Xcode 10中

//This is your str
let str = "This is my String" //Here replace with your string

选项1

let items = str.components(separatedBy: " ")//Here replase space with your value and the result is Array.
//Direct single line of code
//let items = "This is my String".components(separatedBy: " ")
let str1 = items[0]
let str2 = items[1]
let str3 = items[2]
let str4 = items[3]
//OutPut
print(items.count)
print(str1)
print(str2)
print(str3)
print(str4)
print(items.first!)
print(items.last!)

选项2

let items = str.split(separator: " ")
let str1 = String(items.first!)
let str2 = String(items.last!)
//Output
print(items.count)
print(items)
print(str1)
print(str2)

选项3

let arr = str.split {$0 == " "}
print(arr)

选项4

let line = "BLANCHE:   I don't want realism. I want magic!"
print(line.split(separator: " "))
// Prints "["BLANCHE:", "I", "don\'t", "want", "realism.", "I", "want", "magic!"]"

通过Apple文档。。。。

let line = "BLANCHE:   I don't want realism. I want magic!"
print(line.split(separator: " "))
// Prints "["BLANCHE:", "I", "don\'t", "want", "realism.", "I", "want", "magic!"]"

print(line.split(separator: " ", maxSplits: 1))//This can split your string into 2 parts
// Prints "["BLANCHE:", "  I don\'t want realism. I want magic!"]"

print(line.split(separator: " ", maxSplits: 2))//This can split your string into 3 parts

print(line.split(separator: " ", omittingEmptySubsequences: false))//array contains empty strings where spaces were repeated.
// Prints "["BLANCHE:", "", "", "I", "don\'t", "want", "realism.", "I", "want", "magic!"]"

print(line.split(separator: " ", omittingEmptySubsequences: true))//array not contains empty strings where spaces were repeated.
print(line.split(separator: " ", maxSplits: 4, omittingEmptySubsequences: false))
print(line.split(separator: " ", maxSplits: 3, omittingEmptySubsequences: true))

Swift 4或更高版本

如果您只需要正确设置人名格式，可以使用PersonNameComponentsFormater。

PersonNameComponentsFormater类提供本地化人名组成部分的表示通过PersonNameComponents对象。使用此类创建本地化当向用户显示人名信息时。

// iOS (9.0 and later), macOS (10.11 and later), tvOS (9.0 and later), watchOS (2.0 and later)
let nameFormatter = PersonNameComponentsFormatter()

let name =  "Mr. Steven Paul Jobs Jr."
// personNameComponents requires iOS (10.0 and later)
if let nameComps  = nameFormatter.personNameComponents(from: name) {
    nameComps.namePrefix   // Mr.
    nameComps.givenName    // Steven
    nameComps.middleName   // Paul
    nameComps.familyName   // Jobs
    nameComps.nameSuffix   // Jr.

    // It can also be configured to format your names
    // Default (same as medium), short, long or abbreviated

    nameFormatter.style = .default
    nameFormatter.string(from: nameComps)   // "Steven Jobs"

    nameFormatter.style = .short
    nameFormatter.string(from: nameComps)   // "Steven"

    nameFormatter.style = .long
    nameFormatter.string(from: nameComps)   // "Mr. Steven Paul Jobs jr."

    nameFormatter.style = .abbreviated
    nameFormatter.string(from: nameComps)   // SJ

    // It can also be use to return an attributed string using annotatedString method
    nameFormatter.style = .long
    nameFormatter.annotatedString(from: nameComps)   // "Mr. Steven Paul Jobs jr."
}

编辑/更新：

Swift 5或更高版本

对于按非字母字符拆分字符串，我们可以使用新的Character属性isLetter：

let fullName = "First Last"

let components = fullName.split{ !$0.isLetter }
print(components)  // "["First", "Last"]\n"

var fullName = "James Keagan Michael"
let first = fullName.components(separatedBy: " ").first?.isEmpty == false ? fullName.components(separatedBy: " ").first! : "John"
let last =  fullName.components(separatedBy: " ").last?.isEmpty == false && fullName.components(separatedBy: " ").last != fullName.components(separatedBy: " ").first ? fullName.components(separatedBy: " ").last! : "Doe"

不允许使用相同的名字和姓氏如果全名无效，则取占位符值“John Doe”