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The instantiation principle, the idea that in order for a property to exist, it must be had by some object or substance; the instance being a specific object rather than the idea of it; Universal instantiation; An instance (predicate logic), a statement produced by applying universal instantiation to a universal statement
The instantiation principle or principle of instantiation or principle of exemplification is the concept in metaphysics and logic (first put forward by David Malet Armstrong) that there can be no uninstantiated or unexemplified properties (or universals). In other words, it is impossible for a property to exist which is not had by some object.
When created, an occurrence is said to have been instantiated, and both the creation process and the result of creation are called instantiation. Examples [ edit ]
In predicate logic, universal instantiation [1] [2] [3] (UI; also called universal specification or universal elimination, [citation needed] and sometimes confused with dictum de omni) [citation needed] is a valid rule of inference from a truth about each member of a class of individuals to the truth about a particular individual of that class.
It is a kind of lazy evaluation that refers specifically to the instantiation of objects or other resources. This is typically accomplished by augmenting an accessor method (or property getter) to check whether a private member, acting as a cache, has already been initialized. If it has, it is returned straight away.
How can an object's instantiation be deferred to a subclass? Create an object by calling a factory method instead of directly calling a constructor. This enables the creation of subclasses that can change the way in which an object is created (for example, by redefining which class to instantiate).
In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns , which describe how to solve recurring problems in object-oriented software. [ 1 ]
factory method pattern, which allows a class to defer instantiation to subclasses. [ 4 ] prototype pattern , which specifies the kind of object to create using a prototypical instance, and creates new objects by cloning this prototype.