1.?NSDictionary->JSON
NSDictionary *jsonDic = @{};
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonDic options:0 error:nil]; // 如果不想要 JSON 字符串里帶空格或換行等 options 傳 0
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
2.?JSON->NSDictionary
NSString *jsonString = @"";
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *jsonDic = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:nil];
3.?NSJSONReadingOptions 枚舉說明
NSJSONReadingMutableContainers //?Specifies that arrays and dictionaries are created as mutable objects.
NSJSONReadingMutableLeaves //?Specifies that leaf strings in the JSON object graph are created as instances of NSMutableString.
NSJSONReadingAllowFragments //?Specifies that the parser should allow top-level objects that are not an instance of NSArray or NSDictionary.
