url字符串中具有特殊功能的特殊字符的字符串，或者中文字符,作為參數用GET方式傳遞時，需要用urlencode處理一下

//URLEncode

? +(NSString*)encodeString:(NSString*)unencodedString{

? ? if([[[UIDevicecurrentDevice]systemVersion]floatValue] >=9.0) {

? ? ? ? ? ? return[unencodedString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLPathAllowedCharacterSet]];

}

NSString*encodedString = (NSString*)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,(CFStringRef)unencodedString,NULL,(CFStringRef)@"!*'();:@&=+$,/?%#[]",kCFStringEncodingUTF8));

returnencodedString;
}

//URLDEcode

-(NSString *)decodeString:(NSString*)encodedString

{

//NSString *decodedString = [encodedString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding ];

NSString *decodedString? = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(NULL,

(__bridge CFStringRef)encodedString,

CFSTR(""),

CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding));

return decodedString;

有用戶反饋，說iOS9之后，CFURLCreateStringByAddingPercentEscapes這個方法廢棄，所以根據官方的描述 替換使用stringByAddingPercentEncodingWithAllowedCharacters 這個方法。

stringByAddingPercentEncodingWithAllowedCharacters 需要傳遞參數NSCharacterSet 。