这是@Fattie的“THE REASONABLE SOLUTION”的新版本，在Swift 4.1的一个名为String+Email.swift的新文件中测试:

import Foundation

extension String {
    private static let __firstpart = "[A-Z0-9a-z]([A-Z0-9a-z._%+-]{0,30}[A-Z0-9a-z])?"
    private static let __serverpart = "([A-Z0-9a-z]([A-Z0-9a-z-]{0,30}[A-Z0-9a-z])?\\.){1,5}"
    private static let __emailRegex = __firstpart + "@" + __serverpart + "[A-Za-z]{2,6}"

    public var isEmail: Bool {
        let predicate = NSPredicate(format: "SELF MATCHES %@", type(of:self).__emailRegex)
        return predicate.evaluate(with: self)
    }
}

所以它的用法很简单:

let str = "mail@domain.com"
if str.isEmail {
    print("\(str) is a valid e-mail address")
} else {
    print("\(str) is not a valid e-mail address")
}

我只是不喜欢向String对象添加func，因为作为电子邮件地址是它们固有的(或不是)。根据我的理解，Bool属性比func更适合。

@JeffersonBe的答案是接近的，但如果字符串是“包含someone@something.com一个有效的电子邮件”，这不是我们想要的。下面是String上的一个扩展，它工作得很好(并且允许测试有效的phoneNumber和其他数据检测器来引导。

/// Helper for various data detector matches.
/// Returns `true` iff the `String` matches the data detector type for the complete string.
func matchesDataDetector(type: NSTextCheckingResult.CheckingType, scheme: String? = nil) -> Bool {
    let dataDetector = try? NSDataDetector(types: type.rawValue)
    guard let firstMatch = dataDetector?.firstMatch(in: self, options: NSRegularExpression.MatchingOptions.reportCompletion, range: NSRange(location: 0, length: length)) else {
        return false
    }
    return firstMatch.range.location != NSNotFound
        // make sure the entire string is an email, not just contains an email
        && firstMatch.range.location == 0
        && firstMatch.range.length == length
        // make sure the link type matches if link scheme
        && (type != .link || scheme == nil || firstMatch.url?.scheme == scheme)
}
/// `true` iff the `String` is an email address in the proper form.
var isEmail: Bool {
    return matchesDataDetector(type: .link, scheme: "mailto")
}
/// `true` iff the `String` is a phone number in the proper form.
var isPhoneNumber: Bool {
    return matchesDataDetector(type: .phoneNumber)
}
/// number of characters in the `String` (required for above).
var length: Int {
    return self.characters.count
}

或者你可以扩展可选文本UITextField:

使用方法:

if  emailTextField.text.isEmailValid() {
      print("email is valid")
}else{
      print("wrong email address")
}

扩展:

extension Optional where Wrapped == String {
    func isEmailValid() -> Bool{
        guard let email = self else { return false }
        let emailPattern = "[A-Za-z-0-9.-_]+@[A-Za-z0-9]+\\.[A-Za-z]{2,3}"
        do{
            let regex = try NSRegularExpression(pattern: emailPattern, options: .caseInsensitive)
            let foundPatters = regex.numberOfMatches(in: email, options: .anchored, range: NSRange(location: 0, length: email.count))
            if foundPatters > 0 {
                return true
            }
        }catch{
            //error
        }
        return false
    }
}

Swift 5中最简单的方法

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

例子

"kenmueller0@gmail.com".isValidEmail

返回……

true

对于那些还在寻找答案的人，请看看下面的框架;

ATGvalidator

它是一个基于规则的验证框架，可以处理大部分开箱即用的验证。最重要的是，它有表单验证器，支持同时验证多个文本字段。

要验证电子邮件字符串，请使用以下方法;

"abcd.hhs@some.com".satisfyAll(rules: [StringRegexRule.email]).status

如果你想验证从文本字段的电子邮件，尝试下面的代码;

textfield.validationRules = [StringRegexRule.email]
textfield.validationHandler = { result in
    // This block will be executed with relevant result whenever validation is done.
    print(result.status, result.errors)
}
// Below line is to manually trigger validation.
textfield.validateTextField()

如果您想在文本框中输入或当焦点更改到另一个字段时验证它，请添加以下行之一;

textfield.validateOnInputChange(true)
// or
textfield.validateOnFocusLoss(true)

请在链接处查看自述文件以获取更多用例。

我为输入验证设计了一个库，其中一个“模块”可以让你轻松地验证一堆东西…

例如，要验证一封电子邮件:

let emailTrial = Trial.Email
let trial = emailTrial.trial()

if(trial(evidence: "test@test.com")) {
   //email is valid
}

SwiftCop是图书馆…希望能有所帮助!