Swift 中的字符串比较是如何发生的 [英] How String Comparison happens in Swift

问题描述

在这个例子中:

var str1 = "hello"
var str2 = "Hello"

if str1 < str2 { print("hello is less than Hello")}
else {print("hello is more than Hello")}

根据什么发现str1大于str2?

on what basis it is found that str1 is greater than str2?

推荐答案

Swift 字符串根据Unicode 整理算法，这意味着(有效地)

Swift strings are compared according to the Unicode Collation Algorithm, which means that (effectively),

• 每个字符串都放入"Unicode 规范化表格 D",
• 按字典顺序比较这些分解"字符串的 Unicode 标量值.

在您的示例中，"hello" 和 "Hello" 具有 Unicode 值

In your example, "hello" and "Hello" have the Unicode values

hello: U+0068, U+0065, U+006C, U+006C, U+006F 
Hello: U+0048, U+0065, U+006C, U+006C, U+006F 

因此 "Hello" <你好".

规范化"或分解"是相关的，例如对于字符带有变音符号.例如，

The "normalization" or "decomposing" is relevant e.g. for characters with diacritical marks. As an example,

a = U+0061
ä = U+00E4
b = U+0062

有分解形式

a: U+0061
ä: U+0061, U+0308  // LATIN SMALL LETTER A + COMBINING DIAERESIS
b: U+0062

因此 "a" <啊"<"b".

有关更多详细信息和示例，请参阅 Swift 中的字符串和字符比较不区分区域设置是什么意思?

For more details and examples, see What does it mean that string and character comparisons in Swift are not locale-sensitive?

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