composite

Composite Design Pattern

Videos

Section	Video Links
Composite Overview
Composite Use Case
Conditional Expressions

Book

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Overview

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Terminology

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Composite UML Diagram

Source Code

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Output

python ./composite/composite_concept.py

LEAF_A          id:2050574298848
LEAF_B          id:2050574298656
COMPOSITE_1     id:2050574298272
COMPOSITE_2     id:2050574298128

<Leaf>          id:2050574298656        Parent: None
<Composite>     id:2050574298128        Parent: None    Components:2
<Leaf>          id:2050574298848        Parent: 2050574298128
<Composite>     id:2050574298272        Parent: 2050574298128   Components:0

Composite Example Use Case

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Composite Example UML Diagram

Output

python ./composite/client.py
<DIR>  root             id:2028913323984        Components: 4
..<FILE> abc.txt        id:2028913323888        Parent: 2028913323984
..<FILE> 123.txt        id:2028913323792        Parent: 2028913323984
..<DIR>  folder_a       id:2028913432848        Components: 1
....<FILE> xyz.txt      id:2028913433088        Parent: 2028913432848
..<DIR>  folder_b       id:2028913433184        Components: 1
....<FILE> 456.txt      id:2028913434432        Parent: 2028913433184

<DIR>  root             id:2028913323984        Components: 3
..<FILE> abc.txt        id:2028913323888        Parent: 2028913323984
..<FILE> 123.txt        id:2028913323792        Parent: 2028913323984
..<DIR>  folder_b       id:2028913433184        Components: 2
....<FILE> 456.txt      id:2028913434432        Parent: 2028913433184
....<DIR>  folder_a     id:2028913432848        Components: 1
......<FILE> xyz.txt    id:2028913433088        Parent: 2028913432848

New Coding Concepts

Conditional Expressions (Ternary Operators).

In /composite/composite_concept.py, there are two conditional expressions.

Conditional expressions an alternate form of if/else statement.

id(self.reference_to_parent) if self.reference_to_parent is not None else None

If the self.reference_to_parent is not None, it will return the memory address (id) of self.reference_to_parent, otherwise it returns None.

This conditional expression follows the format

value_if_true if condition else value_if_false

eg,

SUN = "bright"
SUN_IS_BRIGHT = True if SUN == "bright" else False
print(SUN_IS_BRIGHT)

or

ICE_IS_COLD = True
ICE_TEMPERATURE = "cold" if ICE_IS_COLD == True else "hot"
print(ICE_TEMPERATURE)

or

CURRENT_VALUE = 99
DANGER = 100
ALERTING = True if CURRENT_VALUE >= DANGER else False
print(ALERTING)

Visit https://docs.python.org/3/reference/expressions.html#conditional-expressions for more examples of conditional expressions.

Summary

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