Assignment 2 Tips

Assignment 2 Tips

Blog Posts

• Follow the template in the spec and attach the merge request to the correct task
• Tutors will not have enough time to look through your codebase for things not mentioned in the blogs
• Make it easy for us to award you marks 

Assignment 2 Tips

Task 1 Part f)

• Address all 3 problems mentioned in the spec
• Find and resolve more problems for higher marks
• Do not intentionally write bad code in earlier parts and refactor them in this section
• Do not refactor to resolve a problem that does not exist yet

Design Smells

• If you think you have found a smell, make sure to double check here: Code Smells (refactoring.guru)

Assignment 2 Tips

Composite Pattern

Composite Pattern

What is it?

Structural design pattern that allow objects to be composed into a tree structure such that individual objects and composites of such objects can be treated in the same way.

When to use?

Model a group of classes that forms a hierarchy

Composite Pattern

In Unix based operating systems, directories are just files that can contain other files

Composite Pattern

UML Diagram

• Leaf and Composite both implement the same interface
• Instances of Leaf and Composite can be treated as the same
• A Composite can hold more than one Leaf

• Produces a tree-like structure that leans itself very well towards recursion

Composite Pattern

Use the composite pattern to design a simple calculator that can be used to evaluate an arithmetic expression.

Your calculator should be able to:

• Add two expressions
• Subtract two expressions
• Multiply two expressions
• Divide two expressions

Composite Pattern

Tree representation

exp1 = 42 

exp2 = ((1 + 2) - ((3 / 4) * (5))

Composite Pattern

UML Diagram

Factory Pattern

Factory Pattern

Why use it?

• Reduce coupling between client code (creation logic) and the specific classes being instantiated
• Single responsibility principle: construction of every class in the family is handled at the same place
• Open-Closed principle: introducing new classes into the family simply requires a new factory subclass 

What is it?

Creational design pattern that lets you define an interface for creating objects of a family in a superclass but allows subclasses to alter the type of object that will be created.

Factory Pattern

1. Product declares a common interface to all objects creatable by the Creator and its subclasses
2. Concrete products: different implementations of Product 
3. Creator class declares the factory method that can be overriden
4. Concrete Creators override the Creator to construct new types of products

Factory Pattern

Factory Pattern

Refactor the code such that when the characters are created, they are put in a random location in a grid of length of length 5.

Finding Nemo

Design Pattern Edition

In groups, determine a possible design pattern that could used to solve the following problems

Finding Patterns

Finding Patterns

1. Sorting collections of records in different orders

Finding Patterns

1. Sorting collections of records in different orders

• Strategy pattern. In Java, this could be providing a Comparator to Collections.sort

Finding Patterns

1. Sorting collections of records in different orders

• Strategy pattern. In Java, this could be providing a Comparator to Collections.sort

2. Modelling shapes and the ability to combine shapes

Finding Patterns

1. Sorting collections of records in different orders

• Strategy pattern. In Java, this could be providing a Comparator to Collections.sort

2. Modelling shapes and the ability to combine shapes

• Composite pattern. Regular shapes can form the leaves and compound shapes can be formed by combining shapes.

Finding Patterns

3. Updating a UI component when the state of a program changes.

Finding Patterns

3. Updating a UI component when the state of a program changes.

• Observer pattern. The state of the program is the subject and the UI is the observer.