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Pro Pattern Matching
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| import UIKit | |
| // Swift 4.2 Xcode 10 | |
| //: ## Optional Patterns | |
| func aLegacyObjcFunction() -> String! { | |
| return "I wasn't annotated with modern objc conventions!" | |
| } | |
| func myFunction() -> String { | |
| let optionalString = aLegacyObjcFunction() | |
| // Compiles in Swift 4.1, Error in Swift 4.2 | |
| // Value of optional type 'String?' not unwrapped; did you mean to use '!' or '?'? | |
| // return optionalString | |
| switch optionalString { | |
| case let output?: | |
| return "\(output) is a `String`." | |
| case nil: | |
| return "Phew, that could have been segfault." | |
| } | |
| } | |
| //: ## Type Casting and Enumeration Patterns | |
| enum Error: Swift.Error { | |
| case badError(code: Int) | |
| case closeShave(explanation: String) | |
| case unknown | |
| case fatal | |
| } | |
| enum OtherError: Swift.Error { | |
| case base | |
| } | |
| func makeURLRequest() throws { } | |
| func getUserDetails() { | |
| do { | |
| try makeURLRequest() | |
| } | |
| // Enumeration Case Pattern with where clause | |
| catch Error.badError(let code) where code == 50 { | |
| print("\(code)") | |
| } | |
| // Enumeration Case Pattern with associated value | |
| catch Error.closeShave(let explanation) { | |
| print("There's an explanation! \(explanation)") | |
| } | |
| // Type matching pattern | |
| catch let error as OtherError { | |
| print("This \(error) is a base error") | |
| } | |
| // Type Matching Pattern | |
| catch is Error { | |
| print("We don't want to know much more, it must be fatal or unkown") | |
| } | |
| // is Swift.Error. The compiler gives us the variable error for free here | |
| catch { | |
| print(error) | |
| } | |
| } | |
| //: ## If, While, Guard, For-In | |
| let stringAndInt: (String, Int?) = ("Seven", 7) | |
| if case (_, let value?) = stringAndInt { | |
| print("The int value of the string is \(value)") | |
| } | |
| guard case (_, let value?) = stringAndInt else { | |
| print("We have no value, exiting early.") | |
| exit(0) | |
| } | |
| var guess: Int = 0 | |
| while case 0...10 = guess { | |
| // Playgrounds don't support reading from stdin | |
| //guess = Int(readLine()!)! | |
| guess = 11 | |
| } | |
| print("You guessed a number out of the range!") | |
| //: ## A Custom Expression Pattern with Regex | |
| struct Regex: ExpressibleByStringLiteral, Equatable { | |
| fileprivate let expression: NSRegularExpression | |
| init(stringLiteral: String) { | |
| do { | |
| self.expression = try NSRegularExpression(pattern: stringLiteral, options: []) | |
| } catch { | |
| print("Failed to parse \(stringLiteral) as a regular expression, falling back to match everything") | |
| self.expression = try! NSRegularExpression(pattern: ".*", options: []) | |
| } | |
| } | |
| fileprivate func match(_ input: String) -> Bool { | |
| let result = expression.rangeOfFirstMatch(in: input, options: [], range: NSRange(input.startIndex..., in: input)) | |
| return !NSEqualRanges(result, NSMakeRange(NSNotFound, 0)) | |
| } | |
| static let email: Regex = """ | |
| ^(?:[a-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[a-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+)*|\"(?:[\\x01-\\x08\ | |
| \\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@\ | |
| (?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?: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]?|[a-z0-9-]*[a-z0-9]:(?\ | |
| :[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7\ | |
| f])+)\\])$ | |
| """ | |
| static let phone: Regex = "^(\\+\\d{1,2}\\s)?\\(?\\d{3}\\)?[\\s.-]?\\d{3}[\\s.-]?\\d{4}$" | |
| } | |
| extension Regex { | |
| static func ~=(pattern: Regex, value: String) -> Bool { | |
| return pattern.match(value) | |
| } | |
| } | |
| let input = Bool.random() ? "nerd@bignerdranch.com" : "(770) 817-6373" | |
| switch input { | |
| case Regex.email: | |
| print("Send \(input) and email!") | |
| case Regex.phone: | |
| print("Give Big Nerd Ranch a call at \(input)") | |
| default: | |
| print("An unknown format.") | |
| } | |
| //: ## Switching on a Pointer Value | |
| var emailTextField: UITextField! | |
| var phoneTextField: UITextField! | |
| var passwordTextField: UITextField! | |
| func validateEmail() -> Bool { return false } | |
| func validatePassword() -> Bool { return false } | |
| func validatePhone() -> Bool { return false } | |
| class MyDelegate: NSObject, UITextFieldDelegate { | |
| func textFieldShouldEndEditing(_ textField: UITextField) -> Bool { | |
| switch textField { | |
| case emailTextField: | |
| return validateEmail() | |
| case phoneTextField: | |
| return validatePhone() | |
| case passwordTextField: | |
| return validatePassword() | |
| default: preconditionFailure("Unaccounted for Text Field") | |
| } | |
| } | |
| } |
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