CardParser

Credit Card Type Parsing for Swift

CardParser is a lightweight utility for identifying major credit card types from in-progress input. This is useful for building responsive credit entry forms and validating input.

Usage

For now, just download and add CardParser.swift to your project.

The Basics

To determine the state of some in-progress text:

switch CardState(fromPrefix: cardString) {

case .identified(let card):
  //do something with card

case .indeterminate(let possibleCards):
  //do something with possibleCards

case .invalid:
  //show some validation error

}

Or if you are just concerned with the validity of some completed input:

guard CardState(fromNumber: cardNumber) != .invalid else {
    //show some validation error
}

Under The Hood

CardParser.swift contains the enums:

• CardType
• CardState

Card Type

CardType encapsulates credit card issuers and their validation/ formatting requirements

enum CardType {
    case amex
    case diners
    case discover
    case jcb
    case masterCard
    case visa
}

You can interact with an extracted card type to update your form:

let visa: CardType = .visa
visa.isPrefixValid("4") //true
visa.isValid("4")       //false
visa.cvvLength          //3
visa.segmentGroupings   //[4, 4, 4, 4]
visa.maxLength          //19

Card State

CardState can be leveraged to identify the CardType (or possible CardTypes) of some input.

enum CardState {
    case identified(CardType)
    case indeterminate([CardType])
    case invalid
}

Use CardState to extract state and type information

CardState(fromPrefix: "4")  //.identified(.visa)
CardState(fromPrefix: "3")  //.indeterminate([.amex, .diners, .jcb])
CardState(fromPrefix: "0")  //.invalid

For example, you may write a method to return a card image for your form:

func cardImage(forState cardState:CardState) -> UIImage? {
    switch cardState {
    case .identified(let cardType):
        switch cardType{
        case .visa:         return #imageLiteral(resourceName: "credit_cards_visa")
        case .masterCard:   return #imageLiteral(resourceName: "credit_cards_mastercard")
        case .amex:         return #imageLiteral(resourceName: "credit_cards_americanexpress")
        case .diners:       return #imageLiteral(resourceName: "credit_cards_diners")
        case .discover:     return #imageLiteral(resourceName: "credit_cards_discover")
        case .jcb:          return #imageLiteral(resourceName: "credit_cards_jcb")
        }
    case .indeterminate: return #imageLiteral(resourceName: "credit_cards_generic")
    case .invalid:      return #imageLiteral(resourceName: "credit_cards_invalid")
    }
}

Author

Jay Clark: [email protected]

License

CardParser is available under the MIT license. See the LICENSE file for more info.