在iOS 9.0之后，以前常用的NSString編碼的方法stringByAddingPercentEscapesUsingEncoding:被棄用了，項目中可能會出現(xiàn)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(qiáng)迫癥的優(yōu)秀程序猿，表示不能忍！

文檔里面是這么說的：

- (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。

這個方法官方文檔是這么說的：

// 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.

最后一句Any characters in allowedCharacters outside of the 7-bit ASCII range are ignored.，意思就是說，任何非7-bit ASCII字符擱到allowedCharacters里面也將被忽略，也就是allowedCharacters里面的字符跟7-bit ASCII字符不會被編碼。

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字符，如這些【`#%^{}"[]|\<>】，如果需要忽略之，需要通過(NSCharacterSet *)allowedCharacters這個參數(shù)指定?？偨Y(jié)如下

[aString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

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

注意：

1. 字符集最后是一個空格！
2. 這里字符集的意思就是，字符串中含有字符集里面的字符將不會被編碼。

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

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

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

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

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

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

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

以上，還在等什么，全局搜索替換吧，消滅??！

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