Drop in user input validation for iOS apps

by iOS Example

Validator

Validator is a user input validation library written in Swift. It's comprehensive, designed for extension, and leaves the UI up to you.

Here's how you might validate an email address:

let emailRule = ValidationRulePattern(pattern: EmailValidationPattern.standard, error: validationError)
"invalid@email,com".validate(emailRule) // -> .invalid(validationError)

... or that a user is over the age of 18:

let eighteenYearsAgo = Date().addingTimeInterval(-568024668)
let drinkingAgeRule = ValidationRuleComparison<Date>(min: eighteenYearsAgo, error: validationError)
let dateOfBirth = Date().addingTimeInterval(-662695446) // 21 years old
dateOfBirth.validate(rule: rule) // -> .valid

... or that a number is within a specified range:

let numericRule = ValidationRuleComparison<Int>(min: 50, max: 100, error: validationError)
42.validate(numericRule) // -> .invalid(validationError)

.. or that a text field contains a valid Visa or American Express card number:

let cardRule = ValidationRulePaymentCard(availableTypes: [.visa, .amex], error: validationError)
paymentCardTextField.validate(cardRule) // -> .valid or .invalid(validationError) depending on what's in paymentCardTextField

Features

  • [x] Validation rules:
    • [x] Required
    • [x] Equality
    • [x] Comparison
    • [x] Length (min, max, range)
    • [x] Pattern (email, password constraints and more...)
    • [x] Contains
    • [x] URL
    • [x] Payment card (Luhn validated, accepted types)
    • [x] Condition (quickly write your own)
  • [x] Swift standard library type extensions with one API (not just strings!)
  • [x] UIKit element extensions
  • [x] Open validation error types
  • [x] An open protocol-oriented implementation
  • [x] Comprehensive test coverage
  • [x] Comprehensive code documentation

Demo

Installation

CocoaPods

pod 'Validator'

Carthage

github "adamwaite/Validator"

Usage

Validator can validate any Validatable type using one or multiple ValidationRules. A validation operation returns a ValidationResult which matches either .valid or .invalid([Error]).

let rule = ValidationRulePattern(pattern: EmailValidationPattern.standard, error: validationError)

let result = "invalid@email,com".validate(rule: rule)
// Note: the above is equivalent to Validator.validate(input: "invalid@email,com", rule: rule)

switch result {
case .valid: print("?")
case .invalid(let failures): print(failures.first?.message)
}

Validation Rules

Required

Validates a type exists (not-nil).

let stringRequiredRule = ValidationRuleRequired<String?>(error: validationError)

let floatRequiredRule = ValidationRuleRequired<Float?>(error: validationError)

Note - You can't use validate on an optional Validatable type (e.g. myString?.validate(aRule...) because the optional chaining mechanism will bypass the call. "thing".validate(rule: aRule...) is fine. To validate an optional for required in this way use: Validator.validate(input: anOptional, rule: aRule).

Equality

Validates an Equatable type is equal to another.

let staticEqualityRule = ValidationRuleEquality<String>(target: "hello", error: validationError)

let dynamicEqualityRule = ValidationRuleEquality<String>(dynamicTarget: { return textField.text ?? "" }, error: validationError)

Comparison

Validates a Comparable type against a maximum and minimum.

let comparisonRule = ValidationRuleComparison<Float>(min: 5, max: 7, error: validationError)

Length

Validates a String length satisfies a minimum, maximum or range.

let minLengthRule = ValidationRuleLength(min: 5, error: validationError)

let maxLengthRule = ValidationRuleLength(max: 5, error: validationError)

let rangeLengthRule = ValidationRuleLength(min: 5, max: 10, error: validationError)

Pattern

Validates a String against a pattern.

ValidationRulePattern can be initialised with a String pattern or a type conforming to ValidationPattern. Validator provides some common patterns in the Patterns directory.

let emailRule = ValidationRulePattern(pattern: EmailValidationPattern.standard, error: validationError)

let digitRule = ValidationRulePattern(pattern: ContainsNumberValidationPattern(), error: someValidationErrorType)

let helloRule = ValidationRulePattern(pattern: ".*hello.*", error: validationError)

Contains

Validates an Equatable type is within a predefined SequenceType's elements (where the Element of the SequenceType matches the input type).

let stringContainsRule = ValidationRuleContains<String, [String]>(sequence: ["hello", "hi", "hey"], error: validationError)

let rule = ValidationRuleContains<Int, [Int]>(sequence: [1, 2, 3], error: validationError)

URL

Validates a String to see if it's a valid URL conforming to RFC 2396.

let urlRule = ValidationRuleURL(error: validationError)

Payment Card

Validates a String to see if it's a valid payment card number by firstly running it through the Luhn check algorithm, and secondly ensuring it follows the format of a number of payment card providers.

public enum PaymentCardType: Int {
    case amex, mastercard, visa, maestro, dinersClub, jcb, discover, unionPay
    ///...

To be validate against any card type (just the Luhn check):

let anyCardRule = ValidationRulePaymentCard(error: validationError)

To be validate against a set of accepted card types (e.g Visa, Mastercard and American Express in this example):

let acceptedCardsRule = ValidationRulePaymentCard(acceptedTypes: [.visa, .mastercard, .amex], error: validationError)

Condition

Validates a Validatable type with a custom condition.

let conditionRule = ValidationRuleCondition<[String]>(error: validationError) { $0.contains("Hello") }

Create Your Own

Create your own validation rules by conforming to the ValidationRule protocol:

protocol ValidationRule {
    typealias InputType
    func validate(input: InputType) -> Bool
    var error: ValidationError { get }
}

Example:

struct HappyRule {
    typealias InputType = String
    var error: ValidationError
    func validate(input: String) -> Bool {
        return input == "?"
    }
}

If your custom rule doesn't already exist in the library and you think it might be useful for other people, then it'd be great if you added it in with a pull request.

Multiple Validation Rules (ValidationRuleSet)

Validation rules can be combined into a ValidationRuleSet containing a collection of rules that validate a type.

var passwordRules = ValidationRuleSet<String>()

let minLengthRule = ValidationRuleLength(min: 5, error: validationError)
passwordRules.add(rule: minLengthRule)

let digitRule = ValidationRulePattern(pattern: .ContainsDigit, error: validationError)
passwordRules.add(rule: digitRule)

Validatable

Any type that conforms to the Validatable protocol can be validated using the validate: method.

// Validate with a single rule:

let result = "some string".validate(rule: aRule)

// Validate with a collection of rules:

let result = 42.validate(rules: aRuleSet)

Extend Types As Validatable

Extend the Validatable protocol to make a new type validatable.

extension Thing : Validatable { }

Note: The implementation inside the protocol extension should mean that you don't need to implement anything yourself unless you need to validate multiple properties.

ValidationResult

The validate: method returns a ValidationResult enum. ValidationResult can take one of two forms:

  1. .valid: The input satisfies the validation rules.
  2. .invalid: The input fails the validation rules. An .invalid result has an associated array of types conforming to ValidationError.

Errors

Initialize rules with any ValidationError to be passed with the result on a failed validation.

Example:

struct User: Validatable {

    let email: String

    enum ValidationErrors: String, ValidationError {
        case emailInvalid = "Email address is invalid"
        var message { return self.rawValue }
    }

    func validate() -> ValidationResult {
        let rule ValidationRulePattern(pattern: .emailAddress, error: ValidationErrors.emailInvalid)
        return email.validate(rule: rule)
    }
}

Validating UIKit Elements

UIKit elements that conform to ValidatableInterfaceElement can have their input validated with the validate: method.

let textField = UITextField()
textField.text = "I'm going to be validated"

let slider = UISlider()
slider.value = 0.3

// Validate with a single rule:

let result = textField.validate(rule: aRule)

// Validate with a collection of rules:

let result = slider.validate(rules: aRuleSet)

Validate On Input Change

A ValidatableInterfaceElement can be configured to automatically validate when the input changes in 3 steps.

  1. Attach a set of default rules:

    let textField = UITextField()
var rules = ValidationRuleSet<String>()
rules.add(rule: someRule)
textField.validationRules = rules

  2. Attach a closure to fire on input change:

    textField.validationHandler = { result in
  switch result {
  case .valid:
	    print("valid!")
  case .invalid(let failureErrors):
	    let messages = failureErrors.map { $0.message }
    print("invalid!", messages)
  }
}

  3. Begin observation:

    textField.validateOnInputChange(enabled: true)

Note - Use .validateOnInputChange(enabled: false) to end observation.

Extend UI Elements As Validatable

Extend the ValidatableInterfaceElement protocol to make an interface element validatable.

Example:

extension UITextField: ValidatableInterfaceElement {

    typealias InputType = String

    var inputValue: String { return text ?? "" }

    func validateOnInputChange(enabled: Bool) {
        switch validationEnabled {
        case true: addTarget(self, action: #selector(validateInputChange), forControlEvents: .editingChanged)
        case false: removeTarget(self, action: #selector(validateInputChange), forControlEvents: .editingChanged)
        }
    }

    @objc private func validateInputChange(_ sender: UITextField) {
        sender.validate()
    }

}

The implementation inside the protocol extension should mean that you should only need to implement:

  1. The typealias: the type of input to be validated (e.g String for UITextField).
  2. The inputValue: the input value to be validated (e.g the text value for UITextField).
  3. The validateOnInputChange: method: to configure input-change observation.

Examples

There's an example project in this repository.

Contributing

Any contributions and suggestions are most welcome! Please ensure any new code is covered with unit tests, and that all existing tests pass. Please update the README with any new features. Thanks!

Contact

@adamwaite

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

GitHub

https://github.com/adamwaite/Validator