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;
    
}