字符串的`endIndex`和`count`是不同的(`endIndex` and `count` of a String are different)

字符串的`endIndex`和`count`是不同的(`endIndex` and `count` of a String are different)

在swift2中， endIndex和String count有何不同？ 它是我用过的代码示例。当所有的字符都是英文的时候，它不会发生。

print("count:",self.Label.text!.characters.count) print("endIndex:",self.Label.text!.characters.endIndex) print("String:",self.Label.text!)

输出：

count: 32 endIndex: 34 String: • (دستور زبان) مفعول‌به، مفعول‌عنه

How is it possible to endIndex and count of a String be different in swift2? its the code sample that I've used.it's not happen when all characters are english only.

print("count:",self.Label.text!.characters.count) print("endIndex:",self.Label.text!.characters.endIndex) print("String:",self.Label.text!)

output :

count: 32 endIndex: 34 String: • (دستور زبان) مفعول‌به، مفعول‌عنه

最满意答案

String.CharacterView.Index的原始值是不相关的，不应该使用。 它的原始值只有String和CharacterView中的含义。

在你的情况下，一些Unicode字符只是将修改相邻字符的字符组合成单个字形。 例如，U + 0300，组合Grave Accent：

let str = "i\u{0300}o\u{0300}e\u{0300}" print("String:",str) print("count:",str.characters.count) print("endIndex:",str.characters.endIndex) var i = str.characters.startIndex while i < str.characters.endIndex { print("\(i):\(str.characters[i])") i = i.successor() }

结果是

String: ìòè count: 3 endIndex: 6 0:ì 2:ò 4:è

The raw value of String.CharacterView.Index is irrelevant and should not be used. Its raw value only has meaning from within String and CharacterView.

In your case, some Unicode characters are merely combining characters that modify adjacent characters to form a single grapheme. For example, U+0300, Combining Grave Accent:

let str = "i\u{0300}o\u{0300}e\u{0300}" print("String:",str) print("count:",str.characters.count) print("endIndex:",str.characters.endIndex) var i = str.characters.startIndex while i < str.characters.endIndex { print("\(i):\(str.characters[i])") i = i.successor() }

results in

String: ìòè count: 3 endIndex: 6 0:ì 2:ò 4:è