class
| A way of categorizing objects based on their behavior and shape.
A class is a definition of a generic object.
In SOM, a class is a special kind of object that can
manufacture other objects that all have a common shape
and exhibit similar behavior.
More precisely, all of the SOM class
objects manufactured by a class have the same memory layout
and share a common set of methods.
New OpenDoc classes can be defined in terms of existing classes
through a technique known as inheritance.
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class method
| A class method of class <X> is a method provided by the metaclass
of class <X>.
Class methods are executed without requiring any
instances of class <X> to exist and are
frequently used to create instances.
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inheritance
| The technique of specifying the shape and behavior of
one class (called a subclass) as incremental differences
from another class
(called the parent class or superclass).
The subclass inherits the parent's state representation
and methods and can provide additional data elements and methods.
The subclass also can provide new functions with
the same method names used by the parent class.
Such a subclass method overrides the parent class method
and will be selected by method resolution on subclass instances.
An overriding method can elect to
call upon the parent class' method as part of its own
implementation
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instance
| (Or object instance).
A specific object, as distinguished
from the abstract definition of an object referred to as its class.
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instance method
| A method that is valid for a particular object.
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metaclass
| A class whose instances are all classes.
In SOM, any class descended from SOMClass is a metaclass.
The methods of a metaclass are sometimes called "class" methods.
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method
| One of the units that make up the behavior of an object.
A method is a combination of a function and a name, such
that many different functions can have the same name.
Which function the name refers to, at any point,
depends on the object that is to execute the method and
is the subject of method resolution.
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object
| The elements of data and function that programs create,
manipulate, pass as arguments, and so forth.
An object is a way of associating specific data values with a
specific set of named functions (called methods) for
a period of time (referred to as the lifetime of the object).
The data values of an object are referred to as its state.
In SOM, objects are created by other objects called classes.
The specification of what
comprises the set of functions and data elements that make up an
object is referred to as the definition of a class.
SOM objects offer a high degree of encapsulation.
This property permits many aspects of the implementation
of an object to change without affecting client programs
that depend on the object's behavior.
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object class
| See class.
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object instance
| See instance.
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parent class
| A class from which another class inherits.
See inheritance.
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subclass
| A class that inherits from another class.
See inheritance.
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superclass
| See parent class.
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