接口级隔离

Question

In my console application I have the class that incapsulates performing long-continued work and I need show the progress to user. Do I need put into object of this class a delegate for interaction with console or to write from class right to screen is ok from the standpoint of application structure?

Answer 1

Do not write to the screen from within that class. I would go with your first suggestion to use events for this - not simply delegates.

You could have an event named OnProgressUpdate which informs the main thread about your current progress state.

Answer 2

I prefer creating an interface IProgressToken which allows setting the current progress, and supplying that to the calculation method.

You can then create an implementation of that interface that writes the progress to the console directly, or every so often, or that updates a progress bar on a form, sending an sms, without having to change the class that performs the calculation.

interface IProgressToken
{
    void SetProgress(float percentage);
}

class MyProgressToken : IProgressToken
{
    void SetProgress(float percentage)
    {
        Console.WriteLine("current progress: " + percentage + "%");
    }
}

// The long running method
ResultType MyCalculationMethod(InputType input, IProgressToken progressToken)
{
    progressToken.SetProgress(0);
    ...
    progressToken.SetProgress(100);
}