CODEWITHSUNDEEP
arraysswiftfor-in-loop
bantukatanaya
bantukatanaya

Reputation: 93

Populate Array with a set of Strings from a for-in loop for Swift

I am kinda stumped on figuring this out. I want to populate an array with the string values that comes from a for-in loop.

Here's an example.

 let names = ["Anna", "Alex", "Brian", "Jack"]

 for x in names {
     println(x)
 }

The current x value would generate 4 string values (Anna, Alex, Brian, Jack).

However I need some advice in going about getting these four values back into an array. Thank you in advance.

Upvotes: 1

Views: 5335

Answers (1)

oisdk
oisdk

Reputation: 10091

Whatever is on the right side of a for - in expression must be a SequenceType. Array, as it happens, can be initialised with any SequenceType. So if you're just doing something like this:

var newArray: [String] = []
for value in exoticSequence {
  newArray.append(value)
}

The same thing can be accomplished (faster), by doing this:

let newArray = Array(exoticSequence)

And it doesn't matter what type exoticSequence is: if the for-in loop worked, Array() will work.

However, if you're applying some kind of transformation to your exoticSequence, or you need some kind of side effect, .map() might be the way to go. .map() over any SequenceType can return an array. Again, this is faster, and more clear:

let exoticSequence = [1, 2, 3]

let newArray = exoticSequence.map {
  value -> Int in
  // You can put whatever would have been in your for-in loop here
  print(value)
  // In a way, the return statement will replace the append function
  let whatYouWouldHaveAppended = value * 2
  return whatYouWouldHaveAppended
}

newArray // [2, 4, 6]

And it's equivalent to:

let exoticSequence = [1, 2, 3]

var newArray: [Int] = []
for value in exoticSequence {
  print(value)
  let whatYouWouldHaveAppended = value * 2
  newArray.append(whatYouWouldHaveAppended)
}

newArray // [2, 4, 6]

Upvotes: 2

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