iOS:data,dic之间的转化

dic->data

   NSMutableDictionary *muDic = [NSMutableDictionary dictionary];
    [muDic setValue:@(89.6) forKey:@"number"];

    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:muDic options:kNilOptions error:nil];
    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

data -> dic

   NSData *jsonData2 = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    NSError *err;
    id dic = [NSJSONSerialization JSONObjectWithData:jsonData2 options:NSJSONReadingMutableContainers error:&err];
    if(err) {
        NSLog(@"json解析失败：%@",err);
    }else{
        NSLog(@"dic is %@",dic);
    }