Swift variable used before initialised

Question

If I write a code like this in swift it says variable x used before initialized. This seems legit in java. Why is this not possible in swift and how do I achieve the same?

  var x:Int
  var y:Int  = 0

  if (y==0) {
      x=0
   }

   if (y==1) {
      x=1
   }

   y=x

Ashish Kakkad · Accepted Answer · 2015-07-03 13:02:14Z

1

You can use ! or ? to define variable without initializing

    var x:Int?
    var y:Int  = 0

    if (y==0) {
        x=0
    }

    if (y==1) {
        x=1
    }

    y=x!

OR

    var x:Int!
    var y:Int  = 0

    if (y==0) {
        x=0
    }

    if (y==1) {
        x=1
    }

    y=x

answered Jul 3, 2015 at 13:02

Ashish Kakkad

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2 Comments

Blazey John Over a year ago

whats the difference between your two examples?

Ashish Kakkad Over a year ago

@BlazeyJohn Refer this for difference between ? and ! stackoverflow.com/questions/25895098/…

vadian · Accepted Answer · 2015-07-03 13:05:30Z

1

A non-optional variable cannot be used before being initialized. But it's possible to even use let when the variable is guaranteed to be initialized before using it

  let x: Int
  var y : Int = 0

  if (y==0) {
      x=0
   } else if (y==1) {
      x=1
   } else {
      x=2
   }

   y=x

answered Jul 3, 2015 at 13:05

vadian

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1 Comment

vadian Over a year ago

Since Swift 1.2 this expression is valid: developer.apple.com/swift/blog/?id=22

Özgür Ersil · Accepted Answer · 2015-07-03 13:00:44Z

0

To use variables, it is an issue that you have to init them or you can force the variable with ! to unwrap or you can init it with optional by using ?. In this case you can use it like that

  var x:Int!  /// var x:Int?
  var y:Int  = 0

   if (y == 0) {
      x=0
   }

   if (y == 1) {
      x=1
   }

answered Jul 3, 2015 at 13:00

Özgür Ersil

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