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<com:TContent ID="body" >
<h1 id="701">Components: Part II</h1>
<com:SinceVersion Version="3.2.3" />
<h2 id="26001">Global events</h2>
<p id="130001" class="block-content">
With the addition of behaviors, a more expansive event model is needed. There
are two new event types (global and dynamic events) as well as a more comprehensive
behavior model that includes class wide behaviors.
</p>
<p id="130002" class="block-content">
A global event is defined by all events whose name starts with 'fx'.
The event name is potentially a method name and is thus case-insensitive. All 'fx' events
are valid as the whole 'fx' event/method space is global in nature. Any object may patch into
any global event by defining that event as a method. Global events have priorities
just like 'on' events; so as to be able to order the event execution. Due to the
nature of all events which start with 'fx' being valid, in effect, every object
has every 'fx' global event. It is simply an issue of tapping into the desired
global event.
</p>
<p id="130003" class="block-content">
A global event that starts with 'fx' can be called even if the object does not
implement the method of the global event. A call to a non-existing 'fx' method
will, at minimal, function and return null. If a method argument list has a first
parameter, it will be returned instead of null. This allows filtering and chaining.
'fx' methods do not automatically install and uninstall. To install and uninstall an
object's global event listeners, call the object's <tt>listen</tt> and
<tt>unlisten</tt> methods, respectively. An object may auto-install its global event
during <tt>__construct</tt> by overriding <tt>getAutoGlobalListen</tt> and returning true.
</p>
<p id="130004" class="block-content">
As of PHP version 5.3, nulled objects without code references will still continue to persist
in the global event queue because <tt>__destruct</tt> is not automatically called. In the common
__destruct method, if an object is listening to global events, then <tt>unlisten</tt> is called.
<tt>unlisten</tt> is required to be manually called before an object is
left without references if it is currently listening to any global events. This includes
class wide behaviors.
</p>
<p id="130005" class="block-content">
An object that contains a method that starts with 'fx' will have those functions
automatically receive those events of the same name after <tt>listen</tt> is called on the object.
</p>
<p id="130006" class="block-content">
An object may listen to a global event without defining an 'fx' method of the same name by
adding an object method to the global event list. For example
</p>
<com:TTextHighlighter CssClass="source block-content">
$component->fxGlobalCheck=$callback; // or $component->OnClick->add($callback);
$component->attachEventHandler('fxGlobalCheck',array($object, 'someMethod'));
</com:TTextHighlighter>
<h2 id="26002">Events between Objects and their behaviors, Dynamic Events</h2>
<p id="130007" class="block-content">
An intra-object/behavior event is defined by methods that start with 'dy'. Just as with
'fx' global events, every object has every dynamic event. Any call to a method that
starts with 'dy' will be handled, regardless of whether it is implemented. These
events are for communicating with attached behaviors.
</p>
<p id="130008" class="block-content">
Dynamic events can be used in a variety of ways. They can be used to tell behaviors
when a non-behavior method is called. Dynamic events could be used as data filters.
They could also be used to specify when a piece of code is to be run, eg. should the
loop process be performed on a particular piece of data. In this way, some control
is handed to the behaviors over the process and/or data.
</p>
<p id="130009" class="block-content">
If there are no handlers for an 'fx' or 'dy' event, it will return the first
parameter of the argument list. If there are no arguments, these events
will return null. If there are handlers an 'fx' method will be called directly
within the object. Global 'fx' events are triggered by calling <tt>raiseEvent</tt>.
For dynamic events where there are behaviors that respond to the dynamic events, a
<tt>TCallChain</tt> is developed. A call chain allows the behavior dynamic event
implementations to call further implementing behaviors within a chain.
</p>
<p id="130010" class="block-content">
If an object implements <tt>IDynamicMethods</tt>, all global and object dynamic
events will be sent to <tt>__dycall</tt>. In the case of global events, all
global events will trigger this method. In the case of behaviors, all undefined
dynamic events which are called will be passed through to this method.
</p>
<p id="130011" class="block-content">
<h2 id="26003">Behaviors</h2>
<p id="130012" class="block-content">
There are two types of behaviors. There are individual object behaviors and
there are class wide behaviors. Class behaviors depend upon object behaviors.
</p>
<p id="130013" class="block-content">
When a new class implements <tt>IBehavior</tt> or <tt>IClassBehavior</tt> or
extends <tt>TBehavior</tt> or <tt>TClassBehavior</tt>, it may be added to an
object by calling the object's <tt>attachBehavior</tt>. The behaviors associated
name can then be used to <tt>enableBehavior</tt> or <tt>disableBehavior</tt>
the specific behavior.
</p>
<p id="130014" class="block-content">
All behaviors may be turned on and off via <tt>enableBehaviors</tt> and
<tt>disableBehaviors</tt>, respectively. To check if behaviors are on or off
a call to <tt>getBehaviorsEnabled</tt> will provide the variable.
</p>
<p id="130015" class="block-content">
Attaching and detaching whole sets of behaviors is done using
<tt>attachBehaviors</tt> and <tt>detachBehaviors</tt>. <tt>clearBehaviors</tt>
removes all of an object's behaviors.
</p>
<p id="130016" class="block-content">
<tt>asa</tt> returns a behavior of a specific name. <tt>isa</tt> is the
behavior inclusive function that acts as the PHP operator <tt>instanceof</tt>.
A behavior could provide the functionality of a specific class thus causing
the host object to act similarly to a completely different class. A behavior
would then implement <tt>IInstanceCheck</tt> to provide the identity of the
different class.
</p>
<p id="130017" class="block-content">
Class behaviors are similar to object behaviors except that the class behavior
is the implementation for all instances of the class. A class behavior
will have the object upon which is being called be prepended to the parameter
list. This way the object is known across the class behavior implementation.
</p>
<p id="130018" class="block-content">
Class behaviors are attached using <tt>attachClassBehavior</tt> and detached
using <tt>detachClassBehavior</tt>. Class behaviors are important in that
they will be applied to all new instances of a particular class. In this way
class behaviors become default behaviors to a new instances of a class in
<tt>__construct</tt>. Detaching a class behavior will remove the behavior
from the default set of behaviors created for an object when the object
is instanced.
</p>
<p id="130019" class="block-content">
Class behaviors are also added to all existing instances via the global 'fx'
event mechanism. When a new class behavior is added, the event
<tt>fxAttachClassBehavior</tt> is raised and all existing instances that are
listening to this global event (primarily after <tt>listen</tt> is called)
will have this new behavior attached. A similar process is used when
detaching class behaviors. Any objects listening to the global 'fx' event
<tt>fxDetachClassBehavior</tt> will have a class behavior removed.
</p>
<h2 id="26004">Dynamic Intra-Object Events</h2>
<p id="130020" class="block-content">
Dynamic events start with 'dy'. This mechanism is used to allow objects
to communicate with their behaviors directly. The entire 'dy' event space
is valid. All attached, enabled behaviors that implement a dynamic event
are called when the host object calls the dynamic event. If there is no
implementation or behaviors, this returns null when no parameters are
supplied and will return the first parameter when there is at least one
parameter in the dynamic event.
</p>
<com:TTextHighlighter CssClass="source block-content">
null == $this->dyBehaviorEvent();
5 == $this->dyBehaviorEvent(5); //when no behaviors implement this dynamic event
</com:TTextHighlighter>
<p id="130021" class="block-content">
Dynamic events can be chained together within behaviors to allow for data
filtering. Dynamic events are implemented within behaviors by defining the
event as a method.
</p>
<com:TTextHighlighter CssClass="source block-content">
class TObjectBehavior extends TBehavior {
public function dyBehaviorEvent($param1, $callchain) {
//Do something, eg: $param1 += 13;
return $callchain->dyBehaviorEvent($param1);
}
}
</com:TTextHighlighter>
<p id="130022" class="block-content">
This implementation of a behavior and dynamic event will flow through to the
next behavior implementing the dynamic event. The first parameter is always
return when it is supplied. Otherwise a dynamic event returns null.
</p>
<p id="130023" class="block-content">
In the case of a class behavior, the object is also prepended to the dynamic
event.
</p>
<com:TTextHighlighter CssClass="source block-content">
class TObjectClassBehavior extends TClassBehavior {
public function dyBehaviorEvent($hostobject, $param1, $callchain) {
//Do something, eg: $param1 += $hostobject->getNumber();
return $callchain->dyBehaviorEvent($param1);
}
}
</com:TTextHighlighter>
</p>
<p id="130024" class="block-content">
When calling a dynamic event, only the parameters are passed. The host object
and the call chain are built into the framework.
</p>
<h2 id="26005">Global Event and Dynamic event catching</h2>
<p id="130025" class="block-content">
Given that all global 'fx' events and dynamic 'dy' events are valid and
operational, there is a mechanism for catching events called that are not
implemented (similar to the built-in PHP method <tt>__call</tt>). When
a dynamic or global event is called but a behavior does not implement it,
yet desires to know when an undefined dynamic event is run, the behavior
implements the interface <tt>IDynamicMethods</tt> and method <tt>__dycall</tt>.
</p>
<p id="130026" class="block-content">
In the case of dynamic events, <tt>__dycall</tt> is supplied with the method
name and its parameters. When a global event is raised, via <tt>raiseEvent</tt>,
the method is the event name and the parameters are supplied.
</p>
<p id="130027" class="block-content">
When implemented, this catch-all mechanism is called for event global event event
when implemented outside of a behavior. Within a behavior, it will also be called
when the object to which the behavior is attached calls any unimplemented dynamic
event. This is the fall-back mechanism for informing a class and/or behavior
of when an global and/or undefined dynamic event is executed.
</p>
</com:TContent>
|
