Synopsis:
A callable object is an invokeable object that can be passed to, and returned from other functions.
Examples are .Net defined and custom delegates and lambdas.
A callable object has a specified signature, e.g., return type and parameter type sequence. The caller
has to know the signature in order to successfully use a callable object.
Here is demonstration code that creates an invoker that accepts any of these callable objects.
Code in File CallableObjects.cs
/////////////////////////////////////////////////////////////////////
// CallableObjects.cs - demonstrate callable object invoker //
// //
// Jim Fawcett, CSE681 - Software Modeling and Analysis, Fall 2017 //
/////////////////////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace CallableObjects
{
public class InvokeCallable
{
public void invoke(Action act)
{
act.Invoke();
}
}
class TestCallableObjects
{
string msg_ = "";
delegate void MyDelegate();
void setMsg(string msg) { msg_ = msg; }
void say()
{
Console.Write("\n Hi from {0}", msg_);
}
static void Main(string[] args)
{
Console.Write("\n Demonstrating Invoker of Callable Objects");
Console.Write("\n ===========================================");
TestCallableObjects tco = new TestCallableObjects();
InvokeCallable ic = new InvokeCallable();
// using method is easy
tco.setMsg("class method");
ic.invoke(tco.say);
// using lambda is easy
ic.invoke(() => Console.Write("\n Hi from lambda"));
// using Action delegate is easy
tco.setMsg("Action delegate");
Action act = tco.say;
ic.invoke(act);
// using custom delegate is a bit messy
// - uses reflection to get delegate's bound function
tco.setMsg("custom delegate");
MyDelegate md = new MyDelegate(tco.say);
Type t = md.GetType();
ic.invoke((Action)Delegate.CreateDelegate(typeof(Action), md, "Invoke"));
Console.Write("\n\n");
}
}
}
Delegates Output:
Demonstrating Invoker of Callable Objects =========================================== Hi from class method Hi from lambda Hi from Action delegate Hi from custom delegate Press any key to continue . . .
