CODEWITHSUNDEEP
swifthigher-order-functions
Ramesh
Ramesh

Reputation: 177

Update element in array

How can we update element of an array

Method 1:-Working code:-

var numberWords = ["one", "two", "three"]
   for i in 0..<numberWords.count {
       if numberWords[i] == "two" {
           numberWords[i] = "2"
       }
   }

But I am looking for solution using Swift high order function

Method 2: 

numberWords = numberWords.filter  {
       if $0 == "one" {
           $0 = "1"//cannot assign value $0 is immutable
       }
       return true
    }

Error thrown : Cannot assign value $0 is immutable

Is it possible or Method 1 is only way?

Upvotes: 5

Views: 10712

Answers (2)

JeremyP
JeremyP

Reputation: 86651

Just as a bit of variety, you could write an in place map, which would probably be more efficient for large arrays (see also reduce(into:)).

extension Array 
{
    mutating func mapInPlace(transform: (inout Element) -> Void)
    {
        for i in 0 ..< self.count
        {
            transform(&self[i])
        }
    }
}

var a = ["one", "two", "three"]
a.mapInPlace{ if $0 == "two" { $0 = "2" } }

Upvotes: 5

Larme
Larme

Reputation: 26036

Do not use filter(), it doesn't make sense.
The point of filter is to iterate each elements and tells if you keep it (return true) or not (return false) according to your desires.

Instead, use map():

numberWords = numberWords.map({ return $0 == "one" ? "1" : $0 })

I used a ternary if and explicitly write a "return" (which is not necessary since it's already done "internally" (you need to returns something)), but you can do it more explicitly keeping your previous code:

numberWords = numberWords.map({
    if $0 == "one" {
        return "1"
    }
    return $0 })

map() is more suited for that. You use it if you want to iterate each items and modify it if needed which is what you want to do.

Upvotes: 14

Related Questions