Having only one element of array to be sorted in my case

Question

I have a list of string:

var nameList = ["Apple", "Watermelon", "orange", ...]

The list is returned from backend, order not garanteed.

I only want to have orange to always be the 1st element in array, no need to care the other elements' order.

I try to use nameList.sort { $0 // what to do}, but get stuck, because I only want one element to be the first element.

How to achieve it?

====== UPDATE ======

A followup question. If I have a list of fruit objects, each fruit is a custom struct object:

struct Fruit {
  public let name;
  public let weight;

  init(_ name: String, _ weight: Double) {
     self.name = name
     self.weight = weight
  }

}

Now, I got a list of Fruit:

var fruitList:[Fruit] = getDataFromBackend()

I would like to have the fruit with name "orange" always be the first item, how to do now?

Answer 1

You can find the index of "orange", and swap it into 0-th index:

if let indexOfOrange = nameList.index(of: "orange") {
    if indexOfOrange != 0 {
        swap(&nameList[0], &nameList[indexOfOrange])
    }
}

If the list can have multiple oranges, use this snippet instead:

let sorted = nameList.filter {$0 == "orange"} + nameList.filter {$0 != "orange"}

It concatenates a list of all oranges with the list of all non-oranges.

Answer 2

A slight variation of dasblinkenlight's solution: Move the "orange" element (if present) to the front and preserve the order of the remaining elements:

var nameList = ["Apple", "Watermelon", "orange"]

if let idx = nameList.index(of: "orange"), idx != 0 {
    nameList.insert(nameList.remove(at: idx), at: 0)
}

print(nameList) // ["orange", "Apple", "Watermelon"]

Answer 3

Well, if order of other elements doesn't matter, you can sort like this:

var nameList = ["Apple", "Watermelon", "orange"]
print(nameList.sorted(by: { first, _ in first == "orange" })) // ["orange", "Apple", "Watermelon"] 

In this case we set the first element what we need ("orange") and don't care about others.

Answer 4

I don't know is it the perfect solution for your question or not but you can try using this. It works for me:-

 let nameList : NSMutableArray = (["Apple", "Watermelon", "orange"] as NSArray).mutableCopy() as! NSMutableArray

    if nameList.contains("orange") {
        nameList.remove("orange")
        nameList.insert("orange", at: 0)
    }

Answer 5

Here's a very simple way to use the native sort function for this:

var fruitList = ["Apple", "Watermelon", "orange"]

let orangeFirst = fruitList.sorted{$1 != "orange"}

orangeFirst // ["orange", "Watermelon", "Apple"]

The function you pass to sorted() is expected to response with true if the first parameter goes before the second one. So any value that is not "orange" should go after orange.

Note that if I had used $0 == "orange" the compiler would have complained that it wanted a two parameter function. By using $1 instead, it understands that there is implicitly a $0 and a $1.