NSString 编解码

base64

NSData编码成NSString

NSData *encodeData = [decodeString dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64String = [encodeData base64EncodedStringWithOptions:0];

NSString解码成NSData

NSData *decodedData = [[NSData alloc] initWithBase64EncodedString:base64String options:0];
NSString *decodedString = [[NSString alloc] initWithData:decodedData encoding:NSUTF8StringEncoding];