classes {RGtk2} | R Documentation |
Highly experimental support for constructing new GObject
classes entirely from with R.
gClass(name, parent = "GObject", class_def = NULL, abstract = FALSE) parentHandler(method, obj = NULL, ...) assignProp(obj, pspec, value) getProp(obj, pspec) registerVirtuals(virtuals) unregisterVirtuals(virtuals)
name |
The name of the new class |
parent |
The name of the parent class |
class_def |
A list that defines the new class - please see the details section |
abstract |
If TRUE , the class should not be instantiable. |
method |
The name of the method to invoke in the parent |
obj |
A GObject |
... |
The additional arguments to the parent method |
pspec |
A GParamSpec describing the property |
value |
The value to set on the property |
virtuals |
An environment containing lists where each list contains the names of the virtual methods for the class matching the name of the list |
.
The bulk of the class definition (everything except the name and the parent)
is contained in the class_def
parameter. This includes:
GObject
class.
Functions overriding methods in the same class are grouped together in a list and
are named according to the virtual they override. Each list is a member of the
class_def
list and bears the name of the corresponding class.GSignalFlags
enumeration. The list of signal definitions
has the name .signals
in the class_def
list.GParamSpec
, as created by gParamSpec
.
The list is named .props
in the class_def
list. The property values
are stored in a private environment. To override that behavior or to be notified
(first) upon property changes, simply override the set_property
and
get_property
virtuals in the GObject
class. To override
the implementation of properties defined by an ancestor class, specify their
names in a separate vector named .prop_overrides
. If you override
the setting or getting of properties, you can use assignProp
or
getProp
to conveniently directly assign or get the
value of a property to or from the low-level data structure, respectively.
These functions differ from the normal property accessor mechanism in that
they bypass the property system, thus avoiding recursion. They should
only be used when overriding property handling..initialize
(in class_def
) will be called with the instance
as the only argument..public
,
.protected
, and .private
keys, respectively. The encapsulation
works much the same as Java. Any protected and public functions may be
overriden in a class derived from the defining class. All public fields
are immutable. All function bindings are locked except for private ones. This
means private functions can be replaced.
The above may seem complicated, and it is. Please see the alphaSliderClass
for an example. Also note that the local
function
is convenient for defining static namespaces on the fly. For calling
parent virtuals, use parentHandler
.
assignProp
and getProp
are low-level functions; they should
not be used in place of the conventional GObject
property
mechanism, except in the case mentioned above.
registerVirtuals
and unregisterVirtuals
are meant for use by
packages that bind C GObject classes to R using the RGtk2 system. An example
of such a package is rggobi.
For gClass
, the GType
of the new class.
For getProp
, the value of the property.
This functionality is not for casual users. If you don't know what you're doing you will break things. Otherwise, have fun.
Michael Lawrence