Sorting in swift 3.0

Question

var arr:Array<Dictionary<String, String>> = [["title":"Mrs","name":"Abc"],["title":"Mr","name":"XYZ"]]
arr.sort { (<#[String : String]#>, <#[String : String]#>) -> Bool in
        <#code#>
    }

I have an array of dictionaries with the data format as represented above. I want to sort this array by name key. I did it in older swift like:

arr.sort{$0.name < $1.name}

which is not working anymore. Please let me know how to move ahead with this structure and sort it.

Thanks.

Answer 1

You have an array of dictionaries of the form [String: String] and a dictionary does not have a name property, so $0.name is invalid (in any Swift version).

Retrieving the dictionary value is done via subscripting, e.g. $0["name"], which returns an optional. In Swift 2 you could compare optionals directly (and nil was considered "less" than any non-nil value). Therefore in Swift 2 you could sort the array with

arr.sortInPlace { $0["name"] < $1["name"] }

However, the optional comparison operators have been removed in Swift 3 with the implementation of SE-0121 – Remove Optional Comparison Operators.

Therefore you have to unwrap $0["name"]. If you are 100% sure that every dictionary in the array has a "name" key then you can unwrap forcefully as Ahmad F suggested

arr.sort { $0["name"]! < $1["name"]! }

If that is not guaranteed then provide a default name, e.g. the empty string via the nil-coalescing operator ??:

arr.sort { ($0["name"] ?? "") < ($1["name"] ?? "") }

Example:

var arr = [["title":"Mrs","name":"Abc"], ["title":"Mr","name":"XYZ"], ["title": "Dr"]]
arr.sort { ($0["name"] ?? "") < ($1["name"] ?? "") }
print(arr)
// [["title": "Dr"], ["name": "Abc", "title": "Mrs"], ["name": "XYZ", "title": "Mr"]]

As one can see, the dictionary without a "name" key is ordered first. A simple way to sort entries without name last would be:

arr.sort { ($0["name"] ?? "\u{10FFFF}") < ($1["name"] ?? "\u{10FFFF}") }

Answer 2

Actually, I'm not pretty sure if arr.sort{$0.name < $1.name} worked in "older swift", however, it should be like:

var arr:Array<Dictionary<String, String>> = [["title":"Mr","name":"XYZ"], ["title":"Mrs","name":"Abc"]]

print(arr) // [["name": "XYZ", "title": "Mr"], ["name": "Abc", "title": "Mrs"]]

arr.sort {
    ($0["name"])! < ($1["name"])!
}

print(arr) // [["name": "Abc", "title": "Mrs"], ["name": "XYZ", "title": "Mr"]]

Hope it helped.