Email validation using NSDataDetector

String+EmailValidation.swift

import Foundation

// Adapted from https://www.cocoanetics.com/2014/06/e-mail-validation/

extension String {
	
	var isValidEmail: Bool {
		
		guard !self.characters.isEmpty else {
			return false
		}
		
		let entireRange = NSRange(location: 0, length: self.characters.count)
		
		let types: NSTextCheckingResult.CheckingType = [.link]

		guard let detector = try? NSDataDetector(types: types.rawValue) else {
			return false
		}
		
		let matches = detector.matches(in: self, options: [], range: entireRange)
		
		// should only have a single match
		guard matches.count == 1 else {
			return false
		}
		
		guard let result = matches.first else {
			return false
		}
		
		// result should be a link
		guard result.resultType == .link else {
			return false
		}
		
		// result should be a recognized mail address
		guard result.url?.scheme == "mailto" else {
			return false
		}
		
		// match must be entire string
		guard NSEqualRanges(result.range, entireRange) else {
			return false
		}
		
		// but schould not have the mail URL scheme
		if self.hasPrefix("mailto:") {
			return false
		}
		
		// no complaints, string is valid email address
		return true
	}
	
}

if the string is "MAILTO:[email protected]", then the scheme is "MAILTO", instead of "mailto",
result.url?.scheme.lowercased == "mailto" will be better.

Swift 5

extension String {

    var isValidEmail: Bool {

        guard !isEmpty else {
            return false
        }

        let entireRange = NSRange(location: 0, length: count)

        let types: NSTextCheckingResult.CheckingType = [.link]

        guard let detector = try? NSDataDetector(types: types.rawValue) else {
            return false
        }

        let matches = detector.matches(in: self, options: [], range: entireRange)

        // should only have a single match
        guard matches.count == 1 else {
            return false
        }

        guard let result = matches.first else {
            return false
        }

        // result should be a link
        guard result.resultType == .link else {
            return false
        }

        // result should be a recognized mail address
        guard result.url?.scheme == "mailto" else {
            return false
        }

        // match must be entire string
        guard NSEqualRanges(result.range, entireRange) else {
            return false
        }

        // but schould not have the mail URL scheme
        if hasPrefix("mailto:") {
            return false
        }

        // no complaints, string is valid email address
        return true
    }
}