Question

I have a program which should read commands from the console and depending on the command perform one of several actions. Here is what I have so far:

void ConwayView::listening_commands() {
    string command;

    do {
        cin >> command;

        if ("tick" == command)
        {
            // to do
        }
        else if ("start" == command)
        {
            // to do for start
        }
        ...

    } while (EXIT != command);
}

Using a switch in place of the if statements helps a little if there are a large amount of commands. What patterns do you suggest using to provide the interactive command line?

Answer 1

If the number of command is small and possible parameters are really few, you could keep on with switch case !

If the number of commands increases, consider the command design pattern (which is IMHO some sort of strategy pattern disguised: cf Using a strategy pattern and a command pattern for the differences between command and strategy patterns).

If most of your commands are all sharing a part of the same behaviour, don’t forget the template method pattern.

If the complexity for creating your command objects increases ( i.e. there is complexity in decoding/understanding the input of your command line), you should start looking at the interpreter design pattern

If while designing with the help of the interpreter pattern, you happen to see some complexity ( if the interpreter needs too much work, you see syntax issues and so on ), then you should probably look at DSL, domain specific language, and design your own language that fits (and only fits) to you own inputs.