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"

斯威夫特2.2添加了错误处理和大写字符串：

func setFullName(fullName: String) {
    var fullNameComponents = fullName.componentsSeparatedByString(" ")

    self.fname = fullNameComponents.count > 0 ? fullNameComponents[0]: ""
    self.sname = fullNameComponents.count > 1 ? fullNameComponents[1]: ""

    self.fname = self.fname!.capitalizedString
    self.sname = self.sname!.capitalizedString
}

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、Xcode 10和iOS 12更新100%工作

let fullName = "First Last"    
let fullNameArr = fullName.components(separatedBy: " ")
let firstName = fullNameArr[0] //First
let lastName = fullNameArr[1] //Last

有关更多信息，请参阅此处的Apple文档。

我还没有找到能够处理3个或更多组件名称并支持较旧iOS版本的解决方案。

struct NameComponentsSplitter {

    static func split(fullName: String) -> (String?, String?) {
        guard !fullName.isEmpty else {
            return (nil, nil)
        }
        let components = fullName.components(separatedBy: .whitespacesAndNewlines)
        let lastName = components.last
        let firstName = components.dropLast().joined(separator: " ")
        return (firstName.isEmpty ? nil : firstName, lastName)
    }
}

通过测试用例：

func testThatItHandlesTwoComponents() {
    let (firstName, lastName) = NameComponentsSplitter.split(fullName: "John Smith")
    XCTAssertEqual(firstName, "John")
    XCTAssertEqual(lastName, "Smith")
}

func testThatItHandlesMoreThanTwoComponents() {
    var (firstName, lastName) = NameComponentsSplitter.split(fullName: "John Clark Smith")
    XCTAssertEqual(firstName, "John Clark")
    XCTAssertEqual(lastName, "Smith")

    (firstName, lastName) = NameComponentsSplitter.split(fullName: "John Clark Jr. Smith")
    XCTAssertEqual(firstName, "John Clark Jr.")
    XCTAssertEqual(lastName, "Smith")
}

func testThatItHandlesEmptyInput() {
    let (firstName, lastName) = NameComponentsSplitter.split(fullName: "")
    XCTAssertEqual(firstName, nil)
    XCTAssertEqual(lastName, nil)
}

假设您有一个名为“Hello World”的变量，如果您想将其拆分并存储为两个不同的变量，可以这样使用：

var fullText = "Hello World"
let firstWord = fullText.text?.components(separatedBy: " ").first
let lastWord = fullText.text?.components(separatedBy: " ").last