Fix Warning "C-Style For Statement Is Deprecated" in Swift 3

Fix warning C-style for Statement is deprecated in Swift 3

C-style for loop has been deprecated in Swift 3. You can continue using it for a while, but they will certainly disappear in the future.

You can rewrite your loop to Swift's style:

for i in 0..<len {
    let length = UInt32 (letters.length)
    let rand = arc4random_uniform(length)
    randomString.appendFormat("%C", letters.characterAtIndex(Int(rand)))
}

Since you don't use i at all in the loop's body, you can replace it with:

for _ in 0..<len {
    // do stuffs
}

C-style for statement has been removed in Swift 3 (Continuos error)

Keeping the index is easy with enumerated:

for (i, sender) in senderArray.enumerated() {
    // Can simply use 'sender' here, no need to index into senderArray.
    if sender == userName {
       ...

    // Unchanged lines; 'i' is used as index here.   
    self.message2Array.append(self.messageArray[i])
    self.sender2Array.append(self.senderArray[i])

}

#warning: C-style for statement is deprecated and will be removed in a future version of Swift

Removing for init; comparison; increment {} and also remove ++ and -- easily. and use Swift's pretty for-in loop

   // WARNING: C-style for statement is deprecated and will be removed in a future version of Swift
   for var i = 1; i <= 10; i += 1 {
      print("I'm number \(i)")
   }

---

Swift 2.2:

   // new swift style works well
   for i in 1...10 {
      print("I'm number \(i)")
   }  

---

For decrement index

  for index in 10.stride(to: 0, by: -1) {
      print(index)
  }

Or you can use reverse() like

  for index in (0 ..< 10).reverse() { ... }

---

for float type (there is no need to define any types to index)

 for index in 0.stride(to: 0.6, by: 0.1) {
     print(index)  //0.0 ,0.1, 0.2,0.3,0.4,0.5
 }  

---

Swift 3.0:

From Swift3.0, The stride(to:by:) method on Strideable has been replaced with a free function, stride(from:to:by:)

for i in stride(from: 0, to: 10, by: 1){
    print(i)
}

For decrement index in Swift 3.0, you can use reversed()

for i in (0 ..< 5).reversed() {
    print(i) // 4,3,2,1,0
}

---

Other then for each and stride(), you can use While Loops

var i = 0
while i < 10 {
    i += 1
    print(i)
}

Repeat-While Loop:

var a = 0
repeat {
   a += 1
   print(a)
} while a < 10

check out Control flows in The Swift Programming Language Guide

C-style for statement is deprecated and will be removed in a future version of Swift

Here how you rewrite your code with while cycle:

var viewController: UIViewController? {
    var next: UIView? = self.superview
    while next != nil {
        let responder = next?.nextResponder()
        if let vc = responder as? UIViewController {
            return vc
        }
        next = next?.superview
    }
    return nil
}

c-style for statement deprecated with a twist

Might be best to go with a while loop:

var totalHeight: CGFloat = 0
while totalHeight < 2.0 * Configurations.sharedInstance.heightGame {
    // Loop code goes here

    totalHeight += backgroundImage.size.height
}

What are the advantages Swift deprecates C-style for statement?

For details, see Swift Evolution - Remove C style for-loops

To quote the reasoning:

1. Both for-in and stride provide equivalent behavior using Swift-coherent approaches without being tied to legacy terminology.
2. There is a distinct expressive disadvantage in using for-loops compared to for-in in succinctness
3. for-loop implementations do not lend themselves to use with collections and other core Swift types.
4. The for-loop encourages use of unary incrementors and decrementors, which will be soon removed from the language.
5. The semi-colon delimited declaration offers a steep learning curve from users arriving from non C-like languages
6. If the for-loop did not exist, I doubt it would be considered for inclusion in Swift 3.

In summary: there are better ways (more expressive) than a C-style for-loop to iterate in Swift.

Some examples:

for-in over a range:

for i in 0 ..< 10 {
    //iterate over 0..9
    print("Index: \(i)")
}

for i in (0 ..< 10).reverse() {
    //iterate over 9..0
    print("Index: \(i)")
}

For arrays (and other sequences) we have many options (the following is not a complete list):

let array = ["item1", "item2", "item3"]

array.forEach {
    // iterate over items
    print("Item: \($0)")
}

array.reverse().forEach {
    // iterate over items in reverse order
    print("Item: \($0)")
}

array.enumerate().forEach {
    // iterate over items with indices
   print("Item: \($1) at index \($0)")
}

array.enumerate().reverse().forEach {
    // iterate over items with indices in reverse order
    print("Item: \($1) at index \($0)")
}

for index in array.indices {
    // iterate using a list of indices
    let item = array[index]
    print("Item \(item) at index: \(index)")
}

Also note that if you are converting an array to another array, almost always you want to use array.filter or array.map or a combination of them.

For all Strideable types we can use the stride method to generate indices, for example:

for index in 10.stride(to: 30, by: 5) {
    // 10, 15, 20, 25 (not 30)
    print("Index: \(index)")
} 

for index in 10.stride(through: 30, by: 5) {
    // 10, 15, 20, 25, 30
    print("Index: \(index)")
}

With arrays we can do:

for index in 0.stride(to: array.count, by: 2) {
    // prints only every second item
    let item = array[index]
    print("Item \(item) at index: \(index)")
}

how to rewrite the following for loop in swift 3 syntax?

for i in stride(from: n-2, through: 0, by: -1) {

}

How to fix C-style for statement?

You could convert the for loop into a while loop:

var ptr = ifaddr
while ptr != nil {
    // Do stuff
    ptr = ptr.memory.ifa_next
}

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