The bridge pattern allows us to operate a two part system
which translates an expression of the intent to do work into the actual work to
be performed. It accomplishes this by pairing two different parts of a system
that are dependent on each other for accomplishing a given task.
When discussing the bridge pattern, though, we must be
careful from the outset to distinguish between two part systems. We are not
interested in systems where half of the work is done by one member of the team
and then the other team member takes over half way and finishes the task. For
example, we are not talking about a leer-jet/limousine teams or
commercial-airliner/taxi combinations. In these examples a tangible piece of work
is done by the first team member and this is followed by tangible work done by
the second team member.
The Bridge pattern, instead, looks at situations where the
two team members work hand-in-hand in order to accomplish the task. So we are
interested here in things like printer/cartridge, sim-card/Cell-phone,
Limousine/Chauffeur, Mother/Father, Rim/Tire combinations. Nothing at all can
be accomplished without the member on the left-side of the slash. Neither can
the member on the right-side do anything by itself. Without one or the other
you cannot begin to do anything at all. None can start the job for the other
to finish; they are both powerless without each other.