The Command Pattern

[Brandon Tom]

In the book "Head First Design Patterns", the author says that a command object "encapsulates a request by binding together a set of actions on a specific receiver."

This statement is confusing to me. What is meant by "binding together a set of actions?" (After I typed it, I suppose I understood it a little better, but I'd like to hear in from a different perspective).

Thanks!

[Peer Reynders]

Originally posted by Brandon Tom:
What is meant by "binding together a set of actions?"

"encapsulates a request by binding together                  on                    ."
                                            a set of actions    a specific receiver

It's the "set of actions" that are bound to the receiver, rather than binding the actions to one another.
The "set of actions" are the operations in the Command's execute() method that are executed against the receiver. So the invoking class doesn�t need to know "how" the command is executed nor "who" the command is executed against.

See also Command Design Pattern
[ April 25, 2006: Message edited by: Peer Reynders ]

[Stan James]

I'm finding the "binding ... on a specific receiver" tough to follow. What does that mean?

[Ilja Preuss]

Originally posted by Stan James:
I'm finding the "binding ... on a specific receiver" tough to follow. What does that mean?

Isn't that even "binding together st. on st."? Frankly, I have no idea what that means.

[Peer Reynders]

My wife would blame the "whole language" approach to learning at this point.
"It doesn't have to be perfectly correct, as long as it conveys the intended meaning."
English can be an ambiguous language to begin with (keeping lawyers in a thriving business). Playing it fast and loose doesn't help.