修正警告“c风格声明被弃用”在Swift 3。

I have update Xcode to 7.3 and now I have a warning to the function that I use to create random strings.

我已经将Xcode更新为7.3，现在我对用于创建随机字符串的函数有一个警告。

I have tried to change the for statement with for (i in 0 ..< len){...} however, the warning became an error.

我已经试着把for语句改为for (I in 0 .)< len){…然而，这个警告变成了一个错误。

How can I remove the warning?

我如何删除警告?

static func randomStringWithLength (len : Int) -> NSString {
  let letters : NSString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
  let randomString : NSMutableString = NSMutableString(capacity: len)

  for (var i=0; i < len; i += 1){ // warning
    let length = UInt32 (letters.length)
    let rand = arc4random_uniform(length)
    randomString.appendFormat("%C", letters.characterAtIndex(Int(rand)))
  }
  return randomString
}

4 个解决方案

#1

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.

for循环的c风格已经在Swift 3中被弃用。您可以继续使用它一段时间，但是它们肯定会在将来消失。

You can rewrite your loop to Swift's style:

你可以把你的循环改写成Swift的风格:

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:

因为你不用我在循环的身体里，你可以用:

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

#2

This BLOG saved my life.

这个博客救了我一命。

INCREMENTING

递增

for i in 0 ..< len {

}

DECREMENTING

递减

for i in (0 ..< len).reverse() {

}

NON-SEQUENTIAL INDEXING

非时序的索引

Using where

使用在哪里

for i in (0 ..< len) where i % 2 == 0 {

}

Using striding to or through

用大步走或通过。

for i in 0.stride(to: len, by: 2) {

}

#3

in Swift 3 it's been an error

在Swift 3中，这是一个错误。

some general replacement was posted and just add

一些一般性的替换被发布并添加。

For Swift 3 and need to change the "index"

对于Swift 3，需要更改“索引”

for var index in stride(from: 0, to: 10, by: 1){}

#4

I've had success with the following. You can use the for loop as follows - note that the for loop is inclusive so you may need to check that len is actually greater than 0:

我已经成功了。您可以使用for循环语句—注意for循环是包含在内的，因此您可能需要检查len是否大于0:

for i in 0...len - 1 {
  let length = UInt32 (letters.length)
  let rand = arc4random_uniform(length)
  randomString.appendFormat("%C", letters.characterAtIndex(Int(rand)))
}

Or you can use this:

或者你可以用这个:

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

BTW it appears XCode 7.x does help you to get there but it's a two step process. First you have to change your increment operator from (say) i++ to i += 1 and then XCode warning helps you modify the loop.

顺便说一下，它是XCode 7。x可以帮助你到达那里，但这是两个步骤。首先，你必须改变你的增量运算符，从(比方说)i++到i+ = 1，然后XCode警告帮助你修改循环。

#1