流处理：打印功能C＃

Question

I am relatively new to C#, and have a question regarding output streams.

In my current program I have a class named "batches", which contains some data (batch id, startTime, endTime, duration, etc). I have a list of batches, and would like to be able to print each batch both to the console, and to a file.

I tried to achieve this by writing a Print() method inside of my batch class which prints everything neatly. I would like to pass as an argument to this function either the console or the output file (let's call it fout) so that the function can write to either one. Since both Console and fout use the WriteLine() method like this:

Console.WriteLine("Some text");
fout.WriteLine("Some text");

it seemed like I should give my print function a parameter of type StreamWriter so that I could pass to it either Console or fout, and achieve the same goal as above like this:

Print(Console);
Print(fout);

void Print(StreamWriter stream) {
    stream.WriteLine($"Batch ID: {Id}");
    ...
    ...
}

However, when I try passing console to my print function, I receive an error. I am not familiar enough with streams or how the console works or the inheritance tree which would allow both fout and Console to both be able to use the WriteLine function, but not my print function. Perhaps I just need a different type as a parameter in my function, but I do not know what that type would be.

I am most comfortable programming in c++, and I know that if I were working with that language, it would make most sense to overload the ostream operator; basically, I want a print function that would behave as an ostream operator would.

If anyone needs me to answer any clarifying questions, please let me know and I can do that right away. Thanks in advance!

Answer 1

What you are looking for is a interface , create an ILogger , provide implementation and pass it to your print method. This way, if you want to control the printing logic based on conditions, it would be easy.

static void Main(string[] args)
{
    Batch batch = new Batch() { ID = 1, StartTime = DateTime.Now, EndTime = DateTime.Now, Duration = 10 };

    batch.Print(new ConsoleLogger(), new FileLogger());
}

public class Batch
{
    public int ID { set; get; }
    public DateTime StartTime { set; get; }
    public DateTime EndTime { set; get; }
    public double Duration { set; get; }

    public void Print(ILogger logger)
    {
        logger.Log(this.ToString());
    }

    public void Print(params ILogger[] loggers)
    {
        foreach (ILogger logger in loggers)
        {
            Print(logger);
        }
    }

    public override string ToString()
    {
        return $"ID = {ID} ** StartTime = {StartTime} ** EndTime = {EndTime} ** Duration = {Duration}";
    }
}

public interface ILogger
{
    void Log(string text);
}

public class ConsoleLogger : ILogger
{
    public void Log(string text)
    {
        Console.WriteLine(text);
    }
}

public class FileLogger : ILogger
{
    string filePath = "log.txt";

    public void Log(string text)
    {
        File.AppendAllText(filePath, text + Environment.NewLine);
    }
}