Email Data Detector

EmailDetector.swift

// Inspired by https://www.atomicbird.com/blog/data-detection-in-swift/

import Foundation
import XCTest

fileprivate extension URLComponents {
    init?(_ url: URL) {
        self.init(url: url, resolvingAgainstBaseURL: false)
    }
    
    var isMailToScheme: Bool {
        scheme == "mailto"
    }
}

public extension String {
    private static let linkDetector = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)

    /// Extracts valid email address out of a `String` using `NSDataDetector`
    /// - Returns: Array of extracted ermail addresses. Empty Array if none found
    func extractedEmailAddresses() -> [String] {
        // Could go directly from NSCheckingResult to URLComponents to reduce double iteration to single,
        // but performance gain would be negligible and this looks prettier :)
        String.linkDetector?
            .matches(in: self, options: [], range: NSMakeRange(0, count))
            .compactMap(\.url)
            .compactMap(URLComponents.init)
            .filter(\.isMailToScheme)
            .map(\.path) ?? []
    }
    
    /// Returns true if the `String` contains one or more valid email addresses
    var containsEmailAddress: Bool {
        !extractedEmailAddresses().isEmpty
    }
    
    /// Returns true if `String` is a valid email address and contains no other text
    var isEmailAddress: Bool {
        extractedEmailAddresses().first == self
    }
}

// MARK: Tests
class EmailDetectorTests: XCTestCase {
    
    func testSingleEmail() {
        let singleEmail = "[email protected]"
        
        XCTAssertEqual(singleEmail.extractedEmailAddresses(), [singleEmail])
        XCTAssertTrue(singleEmail.containsEmailAddress)
        XCTAssertTrue(singleEmail.isEmailAddress)
    }
    
    func testMultipleEmails() {
        let multipleEmails = "[email protected] and [email protected]"
        
        XCTAssertEqual(multipleEmails.extractedEmailAddresses(), ["[email protected]", "[email protected]"])
        XCTAssertEqual(multipleEmails.extractedEmailAddresses().count, 2)
        XCTAssertTrue(multipleEmails.containsEmailAddress)
        XCTAssertFalse(multipleEmails.isEmailAddress)
    }
    
    func testNoEmails() {
        let noEmails = "some long string that doesn't contain an email address"

        XCTAssertTrue(noEmails.extractedEmailAddresses().isEmpty)
        XCTAssertFalse(noEmails.containsEmailAddress)
        XCTAssertFalse(noEmails.isEmailAddress)
    }
}

EmailDetectorTests.defaultTestSuite.run()

// MARK: Examples
var foo = "[email protected]"
print(foo.extractedEmailAddresses()) // ["[email protected]"]
print(foo.containsEmailAddress) // true
print(foo.isEmailAddress) // true

foo = "[email protected] and [email protected]"
print(foo.extractedEmailAddresses()) // ["[email protected]", "[email protected]"]
print(foo.containsEmailAddress) // true
print(foo.isEmailAddress) // false

foo = "some long string that doesn't contain an email address"
print(foo.extractedEmailAddresses()) // []
print(foo.containsEmailAddress) // false
print(foo.isEmailAddress) // false