这是Swift 3的扩展

extension String {
    func isValidEmail() -> Bool {
        let emailRegex = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
        return NSPredicate(format: "SELF MATCHES %@", emailRegex).evaluate(with: self)
    }
}

就像这样使用它:

if yourEmailString.isValidEmail() {
    //code for valid email address
} else {
    //code for not valid email address
}

以上大多数正则表达式示例在电子邮件存在基本问题时都无法捕获错误。例如

h..1@nyu.edu -连续的点 ab1234@.nyu.edu - @后面的点 a.bcdnle12.@email.com - @前的点 .abc@email.com -以一个点开始

这是一个字符串扩展，我使用了更严格的规则使用正则表达式。

extension String {
    func isValidEmail() -> Bool {
        let emailRegEx = "^(?!\\.)([A-Z0-9a-z_%+-]?[\\.]?[A-Z0-9a-z_%+-])+@[A-Za-z0-9-]{1,20}(\\.[A-Za-z0-9]{1,15}){0,10}\\.[A-Za-z]{2,20}$"
        let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
        return emailPred.evaluate(with: self)
   }
}

下面是我们如何为它编写测试用例。

XCTAssertFalse("ab1234@.nyu.edu".isValidEmail())
XCTAssertTrue("valid_email@email.com".isValidEmail())

我会使用npredicate:

func isValidEmail(_ email: String) -> Bool {        
    let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"

    let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
    return emailPred.evaluate(with: email)
}

对于Swift 3.0之前的版本:

func isValidEmail(email: String) -> Bool {
    let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"

    let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
    return emailPred.evaluate(with: email)
}

对于Swift 1.2之前的版本:

func isValidEmail(email: String) -> Bool {
    let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"

    if let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx) {
        return emailPred.evaluateWithObject(email)
    }
    return false
}

如果你正在寻找一个干净简单的解决方案，你应该看看https://github.com/nsagora/validation-components。

它包含一个电子邮件验证谓词，很容易集成在你的代码:

let email = "test@example.com"
let rule = EmailValidationPredicate()
let isValidEmail = rule.evaluate(with: email)

在引擎盖后面，它使用RFC 5322 regex (http://emailregex.com):

let regex = "(?:[\\p{L}0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[\\p{L}0-9!#$%\\&'*+/=?\\^_`{|}" +
    "~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\" +
    "x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[\\p{L}0-9](?:[a-" +
    "z0-9-]*[\\p{L}0-9])?\\.)+[\\p{L}0-9](?:[\\p{L}0-9-]*[\\p{L}0-9])?|\\[(?:(?:25[0-5" +
    "]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-" +
    "9][0-9]?|[\\p{L}0-9-]*[\\p{L}0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21" +
    "-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])"

在Swift 5.7中，在Regex类的帮助下，我们可以以简单有效的方式验证电子邮件地址

private func isValidEmail(_ email: String) -> Bool {
      guard let emailRegex = try? Regex("[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}")  
      else { return false }
      return email.firstMatch(of: emailRegex) != nil
   }

我们还可以使用属性包装器来提高效率:

@propertyWrapper
struct EmailPropertyWrapper {
  private var _value: String
  var wrappedValue: String {
    get { return isValidEmail(_value) ? _value : String() }
    set { _value = newValue }
  }
  
  init(email: String) {
    _value = email
  }

  private func isValidEmail(_ email: String) -> Bool {
      guard let emailRegex = try? Regex("[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}")  
      else { return false }
      return email.firstMatch(of: emailRegex) != nil
   }
}

struct User {
  var name: String
  @EmailPropertyWrapper var email: String
  
  func validateProperty() -> Bool {
    if name.isEmpty || email.isEmpty { return false }
    return true
  }
}

let user = User(name: "Sy", email: .init(email: "wwdc@icloud.com"))

print(user.validateProperty())

我更喜欢用扩展名。此外，这个url http://emailregex.com可以帮助您测试regex是否正确。事实上，该站点为某些编程语言提供了不同的实现。我分享了Swift 3的实现。

extension String {
    func validateEmail() -> Bool {
        let emailRegex = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,6}"
        return NSPredicate(format: "SELF MATCHES %@", emailRegex).evaluate(with: self)
    }
}