字典和JSON格式字符串相互转换

+ (NSDictionary *)dictionaryWithJsonString:(NSString *)jsonString {
    
    if (jsonString == nil) {
        return nil;
    }
    
    NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    
    NSError *err;
    
    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData
                         
                                                        options:NSJSONReadingMutableContainers
                         
                                                          error:&err];
    
    if(err) {
        
        NSLog(@"JSON解析失败：%@",err);
        
        return nil;

    }
    return dic;
}

+ (NSString*)dictionaryToJson:(NSDictionary *)dic
{
    
    NSError *parseError = nil;
    
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&parseError];
    
    return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
    
}