iOS字典转JSON串

- (NSString *)convertToJSONString:(NSDictionary *)dict
{
    NSError *error;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingPrettyPrinted error:&error];
    NSString *jsonString = nil;
    if (jsonData) {
        jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
    } else {
        NSLog(@"convertToJsonData-error: %@", error?:@"object is nil");
    }
    return jsonString;
}