Goals

• Using sharing to effectively use a large number of objects.
• Motif's GUI strategy to replace heavyweight widgets with lightweight widgets.

Problems

Designing objects down to the lowest levels of system "granularity" provides optimal flexibility, but can be prohibitively expensive …

Example of the design pattern An object pool in the Python programming language.

"""
Offer a significant performance boost; it is most effective in
situations where the cost of initializing a class instance is high, the
rate of instantiation of …

Example of the design pattern An object pool in the Java programming language.

// ObjectPool Class

public abstract class ObjectPool<T> {
  private long expirationTime;

  private Hashtable<T, Long> locked, unlocked;

  public ObjectPool() {
    expirationTime = 30000; // 30 seconds
    locked = …

Example of the design pattern An object pool in the C ++ programming language.

#include <string>
#include <iostream>
#include <list>
class Resource
{
    int value;
    public:
        Resource()
        {
            value = 0;
        }
        void reset()
        {
            value = 0;
        }
        int …

Goals

• Add additional features and functionality to the object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
• Client-specified decoration of the interface of the main object by recursively wrapping it.
• Wrap the gift, put it in the …

In the Factory Method Pattern, a factory method defines what functions must be available in the non-abstract or concrete factory. These functions must be able to create objects that are extensions of a specific class. Which exact subclass is created …

This pattern is useful when you want to encapsulate the construction of a class and isolate knowledge of the concrete class from the client application through an abstract interface.

Один из примеров этого может возникнуть, если у вас есть объектно-ориентированное …

Goals

• Arrange objects into tree structures to represent entire parts of the hierarchy. The linker allows clients to treat individual objects and compositions of objects in the same way.
• Recursive composition
• "Directories contain entries, each of which can be a …

An example of a factory method in the Python programming language

"""
Define an interface for creating an object, but let subclasses decide
which class to instantiate. Factory Method lets a class defer
instantiation to subclasses.
"""

import abc


class …

In class-based programming, the factory method pattern is a creational pattern that uses factory methods to deal with the problem of creating objects without having to specify the exact class of the object that will be created. This is done …