CODEWITHSUNDEEP
swift
user6401887
user6401887

Reputation:

(Swift) How would one check if a specific index of an array was empty?

var array:[Int] = []
var index = 5

if array[index] == nil {
    array[index] = 1
}

Currently Xcode states that an int can not take the value of nil. So this code doesn't work. Is there any way to produce the same effect or verifying if a specific index is empty?

Upvotes: 1

Views: 2873

Answers (2)

DJohnson
DJohnson

Reputation: 919

Declaring the property as:

var array:[Int] = []

the array property itself can be empty (no values) - as it is when you declare it as you did above, but it cannot contain nil values, so a check for nil shouldn't be necessary.

If you are checking to see if the array is empty, calling array.isEmpty, or checking array.count > 0 should do the trick.

If you need to store empty (non-initialized Int's/nil) in the array, then the array would be declared as:

var array:[Int?] = []

in which case the array could hold integers, or nil values. In this case you would need to safely unwrap the optional prior to using it, such as:

var array:[Int?] = [1, 2, nil, 4]    
for item in array {
      if let item = item {
        print("item is \(item)")
      } else {
        print("item is nil")
      }
    }

    //    item is 1
    //    item is 2
    //    item is nil
    //    item is 4

Upvotes: 0

GoZoner
GoZoner

Reputation: 70245

If the array can hold nil values, then its type must be an optional - as such:

var array:[Int?] = []

In general, when accessing an array based on an index you need to confirm that the index is in range. You might extend Array with

extension Array {
  func ref (i:Index) -> Element? {
    return i < count ? self[i] : nil
  }
}

and then use as:

array.ref(i)

[Note: this will confound nil as 'out of range' with nil as 'value in optional array']

Upvotes: 1

Related Questions