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iOS Generics in Swift Generics and Protocols Extending Generic Types

Richard Sun
Richard Sun
11,257 Points
Posted by Richard Sun
Richard Sun
11,257 Points

Generic Element in Array conforms to PrefixContaining but, according to Xcode, has no func "hasPrefix"

I think I've gotten the code correct for deciding if the Element in the array has the prefix, but the elements in the array that conform to PrefixContaining don't have the function "hasPrefix". What is wrong with my code?

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

extension String: PrefixContaining {}

// Enter code below
extension Array where Element: PrefixContaining {
    func filter(byPrefix prefix: String) -> [Element] {
        var newArray: [Element] = []
        for string in self {
            if (self.hasPrefix(prefix)) {
                newArray.append(string)
            }
        }
        return newArray
    }
}

1 Answer

Jeff McDivitt
Jeff McDivitt
23,970 Points
Jeff McDivitt
Jeff McDivitt
23,970 Points

Hi Richard - Not sure if you have figured this one out already there are a few issue with your code but you are not he right track

extension Array where Element: PrefixContaining {


    func filter(byPrefix prefix: String) -> [Element]{
        var output = [Element]()

        for element in self {
            if (element.hasPrefix(prefix)) == true {
            output.append(element)
            }
        }


    return output
    }
}
Richard Sun
Richard Sun
11,257 Points
Richard Sun
Richard Sun
11,257 Points

Yeah, I realized my mistakes after a bit. I didn't see them until after I posted this question. Thanks for the help