An "object" is a programming principle, where you have little
pockets of functionality and information depicting stuff like users,
pages or a database api, which operate on themselves and on
eachother.
Web servers like Apache destroy served client requests, all objects
are destroyed after a page is served, and this made object oriented
programming rather limited before, serving mainly as a way to
organize code. There are web servers and many alternatives that do
allow a persistent state, although it's usually in single user mode,
and objects float "in nowhere". Most of them only show updates with
each page view, or require something like Java on the client-side.
What gives DutchPIPE the feel and functionality which makes it rise
above the normal concept of a collection of persistent objects, is
the concept of one world for everyone, and the concept of objects
being able to contain objects and be in another object. This is what
makes it an abstracted world, and this allows for a lot of
"auto-magic" to arise for developers. This world concept is much
like the LPMud
(Multi-user Dungeons/Domains/Dimensions by Lars Pensj) concept
I toyed with in the early nineties, and still appeals to me as one
of the most natural and powerful building concepts.
Our world concept is based on just three very important functions
which are available to all objects:
ob->getEnvironment() returns the object which
contains 'ob'ob->getInventory() returns an array of objects
that 'ob' containsob->moveObject(ob2) moves 'ob' into
'ob2'
(Internally, PHP doesn't know about the concept of objects
containing other objects, and this feature is purely simulated.
These functions operate on a global array which maps each object to
the object in which it is contained, its "environment".)
User objects are moved into page objects, that is, the page must be
seen as the environment or location of the user. Other objects, such
as a product object, can then be put in this location, and then the
user can pick it up to "carry" the object, because it is in the same
environment.
Each object inherits a standard object class which defines common
features, which among others simulate our world concept. The three
core methods listed to the left are among these. Others are methods
to set the object's appearance and add actions (see below) to it.
Extending the standard object class, other standard object classes,
such as the user, page or drink class, define our building tools.
Another important concept is that chains of events are triggered by
objects calling eachothers' methods. These chains of events can be
triggered by user actions, or running processes. Each object can
define actions, which can become available to a user when the object
is either a) the user itself, b) in the user's inventory, b) its
environment, c) in the user's environment.
For instance, a page can define the action "print", which becomes
available when the user enters the page, because the user object is
moved into it. The object "beer" defines the action "drink", which,
if the beer is "dropped" in a page, becomes available when the user
enters the page. When you try to drink it, it will then give a
message you need to pick up the beer, if you didn't do so already by
natural reflex. The object enters your inventory, and the drink
action becomes available again. The method in the object which is
linked to the drink action and called when you attempt to drink it,
now sees by a call to getEnvironment() it is indeed
picked up. It calls methods in itself to alter its state into "an
empty beer glass". It calls methods in the user object and in its
environment and other user objects present on the page to
communicate a message or animation which depicts the drinking (this
is an example of how users get messages and such from stuff
triggered by others). If the page depicts a bar, that object could
then decide to offer you a new beer object.
Popular actions are defined by the user object itself, for instance
the actions "get" and "drop" are not defined by each object for
themselves, but by the user object, to operate on other objects.
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