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This JavaScript example implementation provides the toJSON method used by the JSON.stringify() [9] function to serialize the class into a simple string instead of a composite data type. It calls Object.freeze() to make the instance immutable. [10] It overrides the built-in toString() method [11] and the valueOf() method. [12]
One example of how this can be used is to restore an object to its previous state (undo via rollback), another is versioning, another is custom serialization. The memento pattern is implemented with three objects: the originator, a caretaker and a memento. The originator is some object that has an internal state.
Based on the type passed to the PersonFactory object, the original concrete object is returned as the interface IPerson. A factory method is just an addition to the PersonFactory class. It creates the object of the class through interfaces but also allows the subclass to decide which class is instantiated.
This might, for example, help to explicitly enforce certain invariants about certain data in the object staying the same through the lifetime of the object. In some languages, this is done with a keyword (e.g. const in C++ , final in Java ) that designates the field as immutable.
The Math object contains various math-related constants (for example, π) and functions (for example, cosine). (Note that the Math object has no constructor, unlike Array or Date. All its methods are "static", that is "class" methods.) All the trigonometric functions use angles expressed in radians, not degrees or grads.
Java constructors perform the following tasks in the following order: Call the default constructor of the superclass if no constructor is defined. Initialize member variables to the specified values. Executes the body of the constructor. Java permit users to call one constructor in another constructor using this() keyword.
The receiver object owns the method that is called by the command's execute method. The receiver is typically also the target object. For example, if the receiver object is a cursor and the method is called moveUp, then one would expect that the cursor is the target of the moveUp action. On the other hand, if the code is defined by the command ...
Prototype also provides library functions to support classes and class-based objects. [2] In JavaScript, object creation is prototype-based instead: an object creating function can have a prototype property, and any object assigned to that property will be used as a prototype for the objects created with that function. The Prototype framework ...