How to alphabetize an array of objects within Swift 3?

Question

I try to list an array of objects in alphabetic order. I create this simple test, but doesn't know how to achieve this with an array of objects:

let names = ["Martin", "Nick", "Alex", "Ewa", "Barry", "Daniella", "Chris", "Robert", "Andrew"]

func alphabetizeArray(_ s1: String, _ s2: String) -> Bool {
            return s1 < s2
}
let alphabeticNames = names.sorted(by: names)
print(reversedNames)

When I try this for an array of objects I came up with something like this:

func sorterForIDASC(this:People, that:People) -> Bool {
   return this.name > that.name
}
peoples.sort(by: sorterForIDASC)

But this will give me an error of: Binary operator '>' cannot be applied to two 'String?' operands

Anyone suggestions how to solve this. I would examine the names of each object that is from the type of String. I use Swift 3/Xcode8.

Eric Aya · Accepted Answer · 2016-10-23 11:09:12Z

1

If you only need > then implementing > for your optional property is sufficient:

func >(lhs: People, rhs: People) -> Bool {
    if let left = lhs.name, let right = rhs.name {
        return left > right
    }
    return false
}

Now you can use > on an array of your objects:

let result = arrayOfObjects.sorted(by: >)

You could also have your object conform to Equatable and implement at least == and > for the optional property:

struct People: Equatable {
    var name: String?
}

func ==(lhs: People, rhs: People) -> Bool {
    if let left = lhs.name, let right = rhs.name {
        return left == right
    }
    return false
}

func >(lhs: People, rhs: People) -> Bool {
    if let left = lhs.name, let right = rhs.name {
        return left > right
    }
    return false
}

This opens even more possibilities.

edited Oct 23, 2016 at 11:09

answered Oct 23, 2016 at 11:01

Eric Aya

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2 Comments

Caspert Over a year ago

This is working. Thank you. Maybe another question, but in the same context, is this extendable to create groups for each letter, so that can be used in a tableview to use sections of alphabet?

Eric Aya Over a year ago

@Caspert You're welcome. // This will help, sure, for example for filtering, but you will also need more - I think it would be better to ask a new question entirely, exposing your context, if you're struggling with this other task.

jaiswal Rajan · Accepted Answer · 2017-01-07 16:44:06Z

1

In Swift 3.0

you can do that simply like this.

peoples.sort(by: { (this: People, that: People) -> Bool in
    this. name < that. name
})

answered Jan 7, 2017 at 16:44

jaiswal Rajan

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