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.


#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) {

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){

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

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

Sample Image

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

var i = 0
while i < 10 {
i += 1

Repeat-While Loop:

var a = 0
repeat {
a += 1
} 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 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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