我可以申请哪种设计模式来处理命令？

Question

If I have an application of handling commands and processing, is there a suitable design pattern should I use because currently I have a long switch case statements?

switch(command)

{
   case ACK : // process(); break;
   case NAK : // process(); break;
   case POLL: // process(); break;
   ...
}

Answer 1

You could definitely do a few things here. If it's really as simple as tying a command to a value, you can use a simple Dictionary to tie a command name to a delegate that it executes, like:

private static IDictionary<string, Action> _actionsByCommand;

static MyClass() {
    _actionsByCommand[ACK] = Acknowledge;
    _actionsByCommand[POLL] = Poll;
}

private static void Acknowledge() { }
private static void Poll() { }

static void Main() {
    string command = ...;
    _actionsByCommand[command]();
}

Or instead of delegates, you can define classes for each of your commands with a shared base class or interface, and have a Go method of some kind that executes. This would give you the benefit of having additional properties or values tied to each command, if you need it down the road.

Answer 2

Lets say you have three methods with the same signature.

public Func<string, int> Ack = (i) => return 1;
public Func<string, int> Nack= (i) => return 1; 
public Func<string, int> Poll = (i) => return 1; 

and you want to call them without case statement.

public int Call(string commandName)
{
    //Find method
    var method = this.GetType().GetFields().First(x=>x.Name == commandName);
    if (method == null) return null;
    //Convert it to Func
    var m = (Func<string, int>) method.GetValue(this);
    return m.Invoke("");
}

you will use it like.

new MethodRunner().Call("Ack");