iOS全角符与半角符之间的转换

iOS全角符与半角符之间的转换

相关资料:

• 函数『CFString​Transform』中文 详情；

问题

• 1、17-03-15,「有人在群里边问怎么把『半角』符字符串转换成『全角』字符串？」，百度的结果如下：

  • 全角转半角方法如下（略有出入，原文使用的是『MRC』，现在使用的『ARC』）：

      NSString * string = @"ａｂｃｄｅｆｇ，";
    
      NSMutableString *convertedString = [string mutableCopy];
    
      CFStringTransform((CFMutableStringRef)convertedString, NULL, kCFStringTransformFullwidthHalfwidth, false);
    
      NSLog(@"ddc:%@",convertedString);
    

    • 输出结果：ddc:abcdefg,

    • 结果转换成功。

  • 半角转全角只需要把 kCFStringTransformFullwidthHalfwidth 换成kCFStringTransformHiraganaKatakana 即可。

      NSString * string = @"abcdefg,";
    
      NSMutableString *convertedString = [string mutableCopy];
    
      CFStringTransform((CFMutableStringRef)convertedString, NULL, kCFStringTransformHiraganaKatakana, false);
    
      NSLog(@"ddc:%@",convertedString);
    

    • 输出结果：ddc:abcdefg,

    • 结果转换失败。

解决

• 1、首先来看一下函数『CFString​Transform』的说明：

  正如它的 CF 前缀所表述的一样，CFStringTransform 是 Core Foundation 中的一部分。这个函数传入以下参数，并返回一个 Boolean 来表示转换是否成功：

  • string: 需要转换的字符串。由于这个参数是 CFMutableStringRef 类型，一个 NSMutableString 类型也可以通过自由桥接的方式传入。
  • range: 转换操作作用的范围。这个参数是 CFRange，而不是 NSRange。
  • transform: 需要应用的变换。这个参数使用了包含下面将提到的字符串常量的 ICU transform string。
  • reverse: 如有需要，是否返回反转过的变换。

• 2、我们来看一下『Transform identifiers for CFStringTransform』:

    k​CFString​Transform​Strip​Combining​Marks
    The identifier of a transform to strip combining marks (accents or diacritics).
  
    k​CFString​Transform​To​Latin
    The identifier of a transform to transliterate all text possible to Latin script. Ideographs are transliterated as Mandarin Chinese.
  
    k​CFString​Transform​Fullwidth​Halfwidth
    The identifier of a reversible transform to convert full-width characters to their half-width equivalents.
  
    k​CFString​Transform​Latin​Katakana
    The identifier of a reversible transform to transliterate text to Katakana from Latin.
  
    k​CFString​Transform​Latin​Hiragana
    The identifier of a reversible transform to transliterate text to Hiragana from Latin.
  
    k​CFString​Transform​Hiragana​Katakana
    The identifier of a reversible transform to transliterate text to Katakana from Hiragana.
  
    k​CFString​Transform​Mandarin​Latin
    The identifier of a transform to transliterate text to Latin from ideographs interpreted as Mandarin Chinese. This transform is not reversible.
  
    k​CFString​Transform​Latin​Hangul
    The identifier of a reversible transform to transliterate text to Hangul from Latin.
  
    k​CFString​Transform​Latin​Arabic
    The identifier of a reversible transform to transliterate text to Arabic from Latin.
  
    k​CFString​Transform​Latin​Hebrew
    The identifier of a reversible transform to transliterate text to Hebrew from Latin.
  
    k​CFString​Transform​Latin​Thai
    The identifier of a reversible transform to transliterate text to Thai from Latin.
  
    k​CFString​Transform​Latin​Cyrillic
    The identifier of a reversible transform to transliterate text to Cyrillic from Latin.
  
    k​CFString​Transform​Latin​Greek
    The identifier of a reversible transform to transliterate text to Greek from Latin.
  
    k​CFString​Transform​To​XMLHex
    The identifier of a reversible transform to transliterate characters other than printable ASCII to XML/HTML numeric entities.
  
    k​CFString​Transform​To​Unicode​Name
    The identifier of a reversible transform to transliterate characters other than printable ASCII (minus braces) to their Unicode character name in braces.
  
    k​CFString​Transform​Strip​Diacritics
    The identifier of a transform to remove diacritic markings.
  

具体的自己翻译哈啊（附表一部分翻译结果 来源）：

|Transformation	|Input|	Output|

|----------------|-----|--------|

|kCFStringTransformLatinArabic| mrḥbạ| مرحبا |

|kCFStringTransformLatinCyrillic| privet| привет|

|kCFStringTransformLatinGreek| geiá sou| γειά σου|

|kCFStringTransformLatinHangul| annyeonghaseyo|안녕하세요|

|kCFStringTransformLatinHebrew| şlwm| שלום|

|kCFStringTransformLatinHiragana| hiragana| ひらがな|

|kCFStringTransformLatinKatakana |katakana| カタカナ|

|kCFStringTransformLatinThai| s̄wạs̄dī| สวัสดี|

|kCFStringTransformHiraganaKatakana| にほんご| ニホンゴ|

|kCFStringTransformMandarinLatin| 中文| zhōng wén|

• 3、于是乎 kCFStringTransformHiraganaKatakana 实际上是『片假名』与『平假名』之间的转换，『CFString​Transform』函数中的 reverse 参数意思是转换过程是否可逆；

    NSString * string = @"abcdefg,";
  
    NSMutableString *convertedString = [string mutableCopy];
  
    CFStringTransform((CFMutableStringRef)convertedString, NULL, kCFStringTransformFullwidthHalfwidth, true);
  
    NSLog(@"ddc:%@",convertedString);
  

  • 输出结果：ddc:ａｂｃｄｅｆｇ，

  • 结果转换成功。

彩蛋

• 请尝试下列代码：

    NSString * string = @"我是中文";
  
    NSMutableString *convertedString = [string mutableCopy];
  
    CFStringTransform((CFMutableStringRef)convertedString, NULL, kCFStringTransformMandarinLatin, false);
  
    NSLog(@"转换结果:%@",convertedString);
  
    CFStringTransform((CFMutableStringRef)convertedString, NULL, kCFStringTransformStripDiacritics, false);
  
    NSLog(@"转换结果:%@",convertedString);
  

备注

• 请注意不是所有的『Transform identifiers』都支持逆转