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iOS

Dhanish Gajjar
Dhanish Gajjar
20,185 Points
Posted by Dhanish Gajjar
Dhanish Gajjar
20,185 Points

Generics in Swift 3: Final Challenge

It wasn't easy, but little research online, reviewing the videos and listening carefully makes things a lot more clear.

The solution is below, but I encourage reviewing the videos again, it is really important to understand how the extensions work, specially in the case of Arrays.

extension Array where Element: PrefixContaining {
    func filter(byPrefix prefix: String) -> [Element] {
        var output = [Element]()
        for (_, element) in self.enumerated() {
            if element.hasPrefix(prefix) {
                output.append(element)
            }
        }
        return output
    }
}
Dhanish Gajjar
Dhanish Gajjar
20,185 Points
Dhanish Gajjar
Dhanish Gajjar
20,185 Points

Dan Lindsay I was able to, check this. Hope it helps.

4 Answers

Steven Deutsch
Steven Deutsch
21,046 Points
Steven Deutsch
Steven Deutsch
21,046 Points

Hey Dhanish Gajjar,

Let me prefix this... :P ... with the fact that I don't have a Treehouse subscription at the moment, so I cannot participate or test my work for this challenge.

However, might you consider:

extension Array where Element: PrefixContaining {
    func filter(byPrefix prefix: String) -> [Element] {
        var output = [Element]()
        for element in self {
            if element.hasPrefix(prefix) {
                output.append(element)
            }
        }
        return output
    }
}

Calling the enumerated() method on an Array just lets you iterate over the values in that array and their indices.

However, you're not using the index for the value here, and are omitting it with an _. Therefore, I think its best to remove it completely.

Good Luck

Dan Lindsay
Dan Lindsay
39,611 Points
Dan Lindsay
Dan Lindsay
39,611 Points

Brilliant! I had gotten as far as this:

extension Array where Element: PrefixContaining {
    func filter(byPrefix prefix: String) -> [Element] {
       var prefixArray = [Element]()


       return prefixArray
 }
}

I felt it was going to need to be a for loop, with an if statement nested inside, but just wasn't able to figure it out what do do in them. I am reading the documentation now, but it is nice to have a working solution. Thanks so much for sharing, great work!

Dhanish Gajjar
Dhanish Gajjar
20,185 Points
Dhanish Gajjar
Dhanish Gajjar
20,185 Points

How you do you format your code here? I wrap it in 3 backticks, but it doesn't color code properly for me.

Dan Lindsay
Dan Lindsay
39,611 Points
Dan Lindsay
Dan Lindsay
39,611 Points

After the first 3 backticks put swift(or whatever the name of the code you are posting), paste code starting on next line and on the last line just the 3 backticks.

Qasa Lee
Qasa Lee
18,916 Points
Qasa Lee
Qasa Lee
18,916 Points 
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 filteredArray = Array<Element>()
        for element in self {
            if(element.hasPrefix(prefix)) {
                filteredArray.append(element)
            }
        }
        return filteredArray
    }
}

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

This may help, good luck!