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iOS Generics in Swift Generics and Protocols Extending Generic Types

Posted by mark gilchrist
mark gilchrist
Courses Plus Student 33,169 Points

Code doesnt run on treehouse, works on playground

protocol PrefixContaining { func hasPrefix(_ prefix: String) -> Bool }

extension String: PrefixContaining { func hasPrefix(_ prefix: String) -> Bool { return String(self.characters.prefix(prefix.count)) == prefix } }

extension Array where Element : PrefixContaining { func filter(byPrefix prefix: String) -> [Element]{ return self.filter{ $0.hasPrefix(prefix)} } }

let test = ["aa", "ba", "ca", "ab"] let result = test.filter(byPrefix: "a") // result = ["aa", "ab"]

generics.swift 
protocol PrefixContaining {
    func hasPrefix(_ prefix: String) -> Bool
}

extension String: PrefixContaining {
    func hasPrefix(_ prefix: String) -> Bool {
        return String(self.characters.prefix(prefix.count)) == prefix
    }
}

extension Array where Element : PrefixContaining {
    func filter(byPrefix prefix: String) -> [Element]{
        return self.filter{ $0.hasPrefix(prefix)}
    }
}

// Enter code below