Public Member Functions | Public Attributes | List of all members
CountedResource Class Reference
Inheritance diagram for CountedResource:
CursorResource MouseResource InvalidResource

Public Member Functions

def __init__ (self)
def __del__ (self)
def acquire (cls)
def decrementCounter (cls)
def getCount (cls)
def incrementCounter (cls)
def release (cls)

Public Attributes


Detailed Description

This class is an attempt to combine the RAIA idiom with reference
counting semantics in order to model shared resources. RAIA stands
for "Resource Allocation Is Acquisition" (see 'Effective C++' for a
more in-depth explanation)

When a resource is needed, create an appropriate CountedResource
object.  If the resource is already available (meaning another
CountedResource object of the same type already exists), no action
is taken.  Otherwise, acquire() is invoked, and the resource is
allocated. The resource will remain valid until all matching
CountedResource objects have been deleted.  When no objects of
a particular CountedResource type exist, the release() function for
that type is invoked and the managed resource is cleaned up.

    Define a subclass of CountedResource that defines the
    @classmethods acquire() and release().  In these two
    functions, define your resource allocation and cleanup code.

    If you define your own __init__ and __del__ methods, you
    MUST be sure to call down to the ones defined in

    Until we figure out a way to wrangle a bit more functionality
    out of Python, you MUST NOT inherit from any class that has
    CountedResource as its base class. In debug mode, this will
    raise a runtime assertion during the invalid class's call to
    __init__(). If you have more than one resource that you want to
    manage/access with a single object, you should subclass
    CountedResource again. See the example code at the bottom of
    this file to see how to accomplish this (This is useful for
    dependent resources).

Constructor & Destructor Documentation

◆ __init__()

def __init__ (   self)

Reimplemented in CursorResource, and MouseResource.

◆ __del__()

def __del__ (   self)

Reimplemented in CursorResource, and MouseResource.

Member Function Documentation

◆ acquire()

def acquire (   cls)

Reimplemented in InvalidResource, CursorResource, and MouseResource.

◆ decrementCounter()

def decrementCounter (   cls)

◆ getCount()

def getCount (   cls)

◆ incrementCounter()

def incrementCounter (   cls)

◆ release()

def release (   cls)

Reimplemented in InvalidResource, CursorResource, and MouseResource.

Member Data Documentation