Swift Regex

Regex.swift

// Making the NSRegularExpression a little bit more pretty
typealias RegularExpression = NSRegularExpression
extension RegularExpression {
    convenience init?(pattern: String, options: NSRegularExpressionOptions) {
        self.init(pattern: pattern, options: options, error: nil)
    }
    
    convenience init?(pattern: String) {
        self.init(pattern: pattern, options: nil, error: nil)
    }
}

// Used to create regular expressions
prefix operator / { }
prefix func /(str: String) -> RegularExpression {
    return RegularExpression(pattern: str)!
}

// Used to test strings against regex patterns
func ~=(regex: RegularExpression, str: String) -> Bool {
    return regex.firstMatchInString(str, options: nil, range: NSRange(location: 0, length: (str as NSString).length)) != nil
}

// Example

func isFast(description: String) -> Bool {
    switch description {
    case /"quick|fast|speedy": return true
    default:                   return false
    }
}

isFast("The quick fox jumped over the lazy dog.")        // -> true
isFast("The speedy tiger swam through the deep lagoon.") // -> true
isFast("The slow turtle crawled past the heavy rock.")   // -> false

// Note you can also test outside of switch statements using the ~= operator

let name = "Jaden Geller"
if /"Jaden" ~= name {
    println("Yay!") // -> "Yay!"
}

// Note you can also create your own more complicated regular expression, e.g.
// if RegularExpression(pattern: ..., options: ...) ~= testString { ... }