字符串与UTF8的转换

iOS9之前

字符串->UTF8

NSString *string = [string stringByAddingPercentEscapesUsingEncoding:

NSUTF8StringEncoding];

UTF8->字符串

NSString *string = [string stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

iOS9之后

字符串->UTF8

NSString *string = [string stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

UTF8->字符串

NSString *string = [string stringByRemovingPercentEncoding];