iOS9.0之後NSStringencode方法替換

ro_bber發表於2017-07-18
iOS

在iOS 9.0之後，以前常用的NSString編碼的方法stringByAddingPercentEscapesUsingEncoding:被棄用了，專案中可能會出現一堆如下️：

`stringByAddingPercentEscapesUsingEncoding:` is deprecated: first deprecated in iOS 9.0 – Use -stringByAddingPercentEncodingWithAllowedCharacters: instead, which always uses the recommended UTF-8 encoding, and which encodes for a specific URL component or subcomponent since each URL component or subcomponent has different rules for what characters are valid.

作為一個有強迫症的優秀程式猿，表示不能忍！

文件裡面是這麼說的：

- (nullable NSString *)stringByAddingPercentEscapesUsingEncoding:(NSStringEncoding)enc 
NS_DEPRECATED(10_0, 10_11, 2_0, 9_0, "Use -stringByAddingPercentEncodingWithAllowedCharacters: instead, 
which always uses the recommended UTF-8 encoding, and which encodes for a specific URL component or subcomponent since each URL component or subcomponent has different rules for what characters are valid.");

很明白，用stringByAddingPercentEncodingWithAllowedCharacters:方法替換之。

這個方法官方文件是這麼說的：

// Returns a new string made from the receiver by replacing all characters not in the allowedCharacters set with percent encoded characters. UTF-8 encoding is used to determine the correct percent encoded characters. Entire URL strings cannot be percent-encoded. This method is intended to percent-encode an URL component or subcomponent string, NOT the entire URL string. Any characters in allowedCharacters outside of the 7-bit ASCII range are ignored.

最後一句Any characters in allowedCharacters outside of the 7-bit ASCII range are ignored.，意思就是說，任何非7-bit ASCII字元擱到allowedCharacters裡面也將被忽略，也就是allowedCharacters裡面的字元跟7-bit ASCII字元不會被編碼。

換句話說，上面方法在處理的時候會編碼url的中的非7-bit ASCII字元，如這些【`#%^{}”[]|<>】，如果需要忽略之，需要通過(NSCharacterSet *)allowedCharacters這個引數指定。總結如下

[aString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

//等價於
[aString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet characterSetWithCharactersInString:@"`#%^{}"[]|\<> "]];

注意：

  1. 字符集最後是一個空格！
  2. 這裡字符集的意思就是，字串中含有字符集裡面的字元將不會被編碼。

另外，URL中常用的NSCharacterSet型別定義在分類NSCharacterSet (NSURLUtilities)中，包含字符集如下：

URLHostAllowedCharacterSet      "#%/<>?@^`{|}

URLFragmentAllowedCharacterSet  "#%<>[]^`{|}

URLPasswordAllowedCharacterSet  "#%/:<>?@[]^`{|}

URLPathAllowedCharacterSet      "#%;<>?[]^`{|}

URLQueryAllowedCharacterSet     "#%<>[]^`{|}

URLUserAllowedCharacterSet      "#%/:<>?@[]^`

以上，還在等什麼，全域性搜尋替換吧，消滅️！

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