When should I use Singleton pattern?
Use the Singleton pattern when a class in your program should have just a single instance available to all clients; for example, a single database object shared by different parts of the program. The Singleton pattern disables all other means of creating objects of a class except for the special creation method.
What can I use instead of a Singleton?
The best way is to use a Factory pattern instead. When you construct a new instance of your class (in the factory) you can insert the ‘global’ data into the newly constructed object, either as a reference to a single instance (which you store in the factory class) or by copying the relevant data into the new object.
What is the purpose intent of the composite pattern?
The intent of a composite is to “compose” objects into tree structures to represent part-whole hierarchies. Implementing the composite pattern lets clients treat individual objects and compositions uniformly.
How is composite pattern used in file system?
File System implementations use the composite design pattern as described previously. The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed.
When is composite design pattern a good choice?
If programmers find that they are using multiple objects in the same way, and often have nearly identical code to handle each of them, then composite is a good choice, it is less complex in this situation to treat primitives and composites as homogeneous.
What’s the difference between a composite and a component?
Composite lets clients treat individual objects and compositions of objects uniformly. Component – Component is the abstraction for leafs and composites. It defines the interface that must be implemented by the objects in the composition. For example a file system resource defines move, copy, rename, and getSize methods for files and folders.
How is the client interface used in composite design?
Composite – Composite stores child components and implements child related operations in the component interface. Client – Client manipulates the objects in the composition through the component interface. Client use the component class interface to interact with objects in the composition structure.