如何将字符串拆分为等长的子字符串 [英] How to split a string into substrings of equal length
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问题描述
所以
split("There are fourty-eight characters in this string", 20)
应该返回
["There are fourty-eig", "ht characters in thi","s string"]
如果我使currentIndex = string.startIndex,然后尝试使它比string.endIndex更进一步(),我将收到严重错误:无法递增endIndex",然后再检查currentIndex是否<. string.endIndex,因此下面的代码不起作用
If I make currentIndex = string.startIndex and then try to advance() it further than a string.endIndex, I get "fatal error: can not increment endIndex" before I check if my currentIndex < string.endIndex so the code below doesn't work
var string = "12345"
var currentIndex = string.startIndex
currentIndex = advance(currentIndex, 6)
if currentIndex > string.endIndex {currentIndex = string.endIndex}
推荐答案
我刚刚在SO上回答了类似的问题,并认为我可以提供更简洁的解决方案:
I just answered a similar question on SO and thought I can provide a more concise solution:
func split(str: String, _ count: Int) -> [String] {
return 0.stride(to: str.characters.count, by: count).map { i -> String in
let startIndex = str.startIndex.advancedBy(i)
let endIndex = startIndex.advancedBy(count, limit: str.endIndex)
return str[startIndex..<endIndex]
}
}
雨燕3
func split(_ str: String, _ count: Int) -> [String] {
return stride(from: 0, to: str.characters.count, by: count).map { i -> String in
let startIndex = str.index(str.startIndex, offsetBy: i)
let endIndex = str.index(startIndex, offsetBy: count, limitedBy: str.endIndex) ?? str.endIndex
return str[startIndex..<endIndex]
}
}
雨燕4
更改为while
循环以提高效率,并通过受欢迎的请求使其成为String的扩展名:
Swift 4
Changed to a while
loop for better efficiency and made into a String's extension by popular request:
extension String {
func split(by length: Int) -> [String] {
var startIndex = self.startIndex
var results = [Substring]()
while startIndex < self.endIndex {
let endIndex = self.index(startIndex, offsetBy: length, limitedBy: self.endIndex) ?? self.endIndex
results.append(self[startIndex..<endIndex])
startIndex = endIndex
}
return results.map { String($0) }
}
}
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