[Cs3] State pattern

[Mikhail Nesterenko]

context: the class of objects whose state is being maintained through
	 state class. Delegates behaviors for state class to be
	 implemented.

abstract state: defines the interface of behaviors to be implemented
	 in each state

concrete state: implements behaviors. Part of the implementation is
	 the transition of the context from one (concrete) state to another.

Thanks,
--
Mikhail

Donald Harmon wrote:
> Hello again Mikhail,
> 
> I have a last minute question about the State design pattern.
> 
> In the sample Final exam, question number 5 asks:
> Explain the purpose of the context class, abstract state class and concrete
> state class.
> 
> 
> I just want to make sure I am on the right track with my answer, and if
> not, figure out what the purpose actually is.
> 
> 
> My answer:
> The purpose of the context class is to provide the client with an interface
> to interact with. Context objects have states and pass operations to the
> state class.
> 
> The purpose of the abstract state class is to provide default
> implementations of operations and ensure the correct operation is called
> (concrete state operation) based upon the state of the context.
> 
> The purpose of the concrete state(s) is to define the state change
> operations that affect the state of the context, and provide different
> behavior based upon the state of the context.
>