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In object-oriented programming, the factory method pattern is a design pattern that uses factory methods to deal with the problem of creating objects without having to specify their exact classes. Rather than by calling a constructor , this is accomplished by invoking a factory method to create an object.
In class-based programming, a factory is an abstraction of a constructor of a class, while in prototype-based programming a factory is an abstraction of a prototype object. A constructor is concrete in that it creates objects as instances of one class, and by a specified process (class instantiation), while a factory can create objects by instantiating various classes, or by using other ...
First, the async keyword indicates to C# that the method is asynchronous, meaning that it may use an arbitrary number of await expressions and will bind the result to a promise. [1]: 165–168 The return type, Task<T>, is C#'s analogue to the concept of a promise, and here is indicated to have a result value of type int.
An example would be a static method to sum the values of all the variables of every instance of a class. For example, if there were a Product class it might have a static method to compute the average price of all products. A static method can be invoked even if no instances of the class exist yet.
The class defines the data format or type (including member variables and their types) and available procedures (class methods or member functions) for a given type or class of object. Objects are created by calling a special type of method in the class known as a constructor. Classes may inherit from other classes, so they are arranged in a ...
Before a class derived from an abstract class can be instantiated, all abstract methods of its parent classes must be implemented by some class in the derivation chain. [ 25 ] Most object-oriented programming languages allow the programmer to specify which classes are considered abstract and will not allow these to be instantiated.
It should be possible to define a new operation for (some) classes of an object structure without changing the classes. When new operations are needed frequently and the object structure consists of many unrelated classes, it's inflexible to add new subclasses each time a new operation is required because "[..] distributing all these operations across the various node classes leads to a system ...
One subtlety is that the value of a method call ("message") in a cascade is still the ordinary value of the message, not the receiver. This is a problem when you do want the value of the receiver, for example when building up a complex value. This can be worked around by using the special yourself method that simply returns the receiver: [2]