python-patterns/patterns/structural/composite.py at master · botdigit/python-patterns · GitHub

History

86 lines (63 loc) · 2.24 KB

Raw

#!/usr/bin/env python

# -*- coding: utf-8 -*-

"""

*What is this pattern about?

The composite pattern describes a group of objects that is treated the

same way as a single instance of the same type of object. 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.

*What does this example do?

The example implements a graphic class，which can be either an ellipse

or a composition of several graphics. Every graphic can be printed.

*Where is the pattern used practically?

In graphics editors a shape can be basic or complex. An example of a

simple shape is a line, where a complex shape is a rectangle which is

made of four line objects. Since shapes have many operations in common

such as rendering the shape to screen, and since shapes follow a

part-whole hierarchy, composite pattern can be used to enable the

program to deal with all shapes uniformly.

*References:

https://en.wikipedia.org/wiki/Composite_pattern

https://infinitescript.com/2014/10/the-23-gang-of-three-design-patterns/

*TL;DR80

Describes a group of objects that is treated as a single instance.

"""

class Graphic:

def render(self):

raise NotImplementedError("You should implement this.")

class CompositeGraphic(Graphic):

def __init__(self):

self.graphics = []

def render(self):

for graphic in self.graphics:

graphic.render()

def add(self, graphic):

self.graphics.append(graphic)

def remove(self, graphic):

self.graphics.remove(graphic)

class Ellipse(Graphic):

def __init__(self, name):

self.name = name

def render(self):

print("Ellipse: {}".format(self.name))

if __name__ == '__main__':

ellipse1 = Ellipse("1")

ellipse2 = Ellipse("2")

ellipse3 = Ellipse("3")

ellipse4 = Ellipse("4")

graphic1 = CompositeGraphic()

graphic2 = CompositeGraphic()

graphic1.add(ellipse1)

graphic1.add(ellipse2)

graphic1.add(ellipse3)

graphic2.add(ellipse4)

graphic = CompositeGraphic()

graphic.add(graphic1)

graphic.add(graphic2)

graphic.render()

### OUTPUT ###

# Ellipse: 1

# Ellipse: 2

# Ellipse: 3

# Ellipse: 4

python-patterns/patterns/structural/composite.py at master · botdigit/python-patterns · GitHub

Expand file tree

Breadcrumbs

composite.py

Latest commit

History

Breadcrumbs

composite.py

File metadata and controls