iOS NSDictionary 转Json 去掉换行去掉空格

//dic 转json 如果用系统自带的会出现空格。
+ (NSString *)returnJSONStringWithDictionary:(NSDictionary *)dictionary{

    //系统自带

    //    NSError * error;

    //    NSData * jsonData = [NSJSONSerialization dataWithJSONObject:dictionary options:kNilOptions error:&error];

    //    NSString * jsonStr = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

    //自定义

    NSString *jsonStr = @"{";

    NSArray * keys = [dictionary allKeys];

    for (NSString * key in keys) {

        jsonStr = [NSString stringWithFormat:@"%@\"%@\":\"%@\",",jsonStr,key,[dictionary objectForKey:key]];

    }

    jsonStr = [NSString stringWithFormat:@"%@%@",[jsonStr substringWithRange:NSMakeRange(0, jsonStr.length-1)],@"}"];

    return jsonStr;

}