IOS converts the formatted JSON string into a dictionary

1. - (NSDictionary *)dictionaryWithJsonString:(NSString *)jsonString {  
2.     if (jsonString == nil) {  
3.         return nil;  
4.     }  
5.       
6.     NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];  
7.     NSError *err;  
8.     NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData  
9.                                                         options:NSJSONReadingMutableContainers  
10.                                                           error:&err];  
11.     if(err) {  
12.         NSLog(@"json parsing failed: %@",err);  
13.         return nil;  
14.     }  
15.     return dic;  
16. }