SOLID Design Principles and Good Design Practices

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Questions and Answers

What is the main goal of low coupling in software design?

  • To increase the complexity of the system
  • To enhance the independence of modules (correct)
  • To promote tight integration between components
  • To require frequent modifications

Which principle states a class should have a single responsibility?

  • Liskov Substitution Principle
  • Interface Segregation Principle
  • Single Responsibility Principle (correct)
  • Dependency Inversion Principle

What is the primary benefit of high cohesion in software design?

  • Enhanced functionality of a single module (correct)
  • Increased inter-module interactions
  • Improved system complexity
  • Better module independence

According to the Open/Closed Principle, how should classes be designed?

<p>To be extendable but not modifiable (C)</p> Signup and view all the answers

How can refactoring contribute to good design?

<p>By improving code readability and reducing duplication (C)</p> Signup and view all the answers

What is the preferred level of coupling in software design?

<p>Low coupling (D)</p> Signup and view all the answers

Which principle is part of the SOLID design principles?

<p>Single Responsibility Principle (D)</p> Signup and view all the answers

What does high coupling in a software system indicate?

<p>Many dependencies among classes (C)</p> Signup and view all the answers

According to the Single Responsibility Principle, how many responsibilities should a class have?

<p>One responsibility (D)</p> Signup and view all the answers

What do poor cohesion and overloaded classes typically exhibit?

<p>Too many responsibilities (A)</p> Signup and view all the answers

What is the purpose of applying SOLID principles in software development?

<p>Create code that is flexible (C)</p> Signup and view all the answers

What does a class with high coupling likely require when any single class changes?

<p>Significant changes to many other classes (B)</p> Signup and view all the answers

In the context of cohesion, what indicates good cohesion?

<p>A clear, focused responsibility of a class (C)</p> Signup and view all the answers

What is the primary purpose of improving cohesion in a class?

<p>To relate methods that handle similar concepts. (B)</p> Signup and view all the answers

What does high coupling in software design typically indicate?

<p>Dependence between classes that can lead to issues. (B)</p> Signup and view all the answers

Which of the following best describes the Single Responsibility Principle (SRP)?

<p>A class should be responsible for only one aspect of the functionality. (B)</p> Signup and view all the answers

What is a potential consequence of violating the Single Responsibility Principle?

<p>Changing one part of the class may break other functionalities. (D)</p> Signup and view all the answers

How is a violation of the SRP typically resolved?

<p>By splitting the class into multiple classes with single responsibilities. (D)</p> Signup and view all the answers

Which example illustrates an SRP violation?

<p>A class that processes orders, saves to a database, and emails customers. (A)</p> Signup and view all the answers

What does the Open/Close Principle (OCP) ensure about classes?

<p>Classes can be extended without altering their existing code. (B)</p> Signup and view all the answers

Why might a developer want to apply refactoring techniques?

<p>To eliminate bugs and improve code structure. (D)</p> Signup and view all the answers

What indicates that a class is designed poorly regarding SRP?

<p>The class has multiple unrelated functions and dependencies. (D)</p> Signup and view all the answers

In the example of user management, what was the secondary function that violated SRP?

<p>Displaying user information as HTML. (A)</p> Signup and view all the answers

Flashcards

Single Responsibility Principle (SRP)

A class should only have one reason to change, meaning it should only perform one specific task.

Coupling

The degree of dependence between classes or modules. High coupling means a change in one part affects other parts significantly.

Cohesion

The degree to which the elements of a module belong together. High cohesion means the module focuses on a single task.

SRP Violation Example

A class handling multiple, unrelated tasks (e.g., accepting orders, saving to database, emailing customers).

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Fixing SRP Violation

Splitting a class with multiple responsibilities into multiple classes, each with a single responsibility.

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Open/Closed Principle (OCP)

Software entities (classes, modules, functions, etc.) should be open for extension but closed for modification.

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Example of SRP Violation (E-commerce)

A single class handling order acceptance, database saving, and email sending.

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Example of SRP violation (User Class)

A class for storing user data that also performs validation and display logic

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Fixing SRP violation (User Class)

Separating the functionality of a user class into separate classes for validation and for html rendering.

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HTMLUser class

A separate class specifically focused on formatting user data for HTML output.

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Good software design

Good design reduces complexity, improves flexibility, and makes software easier to maintain.

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Coupling and cohesion

Measures of software design quality. Low coupling means parts of the software are independent; high cohesion means parts work closely together on a single task.

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SOLID principles

A set of object-oriented design principles that help reduce code complexity.

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Single Responsibility Principle

Each class should have only one job to perform.

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Open/Closed Principle

Software entities should be open for extension but closed for modification.

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Bad Cohesion (Fragmented)

A module with elements that are loosely related or perform unrelated tasks, resulting in scattered and difficult-to-understand code.

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Bad Cohesion (Overloaded)

A module that attempts to perform too many tasks, making it complex and difficult to maintain.

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Low Coupling

A design where classes have few dependencies on each other, making changes easier and reducing the impact of modifications.

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SOLID

A set of object-oriented design principles for creating flexible and less complex code.

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Study Notes

Single Responsibility Principle (SRP)

  • SRP states that a class should have only one reason to change.
  • A class should have a single responsibility.
  • This improves cohesion and reduces coupling.
  • Multiple responsibilities in a class can lead to code smells.

SOLID Design

  • SOLID is a set of object-oriented design principles.
  • SOLID principles help to create flexible and maintainable code.
  • SOLID principles aim to minimize complexity.
  • Applying SOLID principles to classes that violate these principles helps create better code.

Goals of Good Design

  • Satisfy requirements.
  • Minimize complexity (using abstraction, decomposition, encapsulation).
  • Maximize flexibility (accomodate changes).
  • Maximize maintainability (understandability, readability).

Characteristics of Good Design

  • Minimal complexity (low coupling, low fan-out).
  • Leanness (minimal code).
  • Stratification (layering).
  • Flexibility (adaptability, extensibility, portability).
  • Maintainability (understandability, readability).

Cohesion

  • Cohesion is a measure of relatedness within a class.
  • High cohesion means everything in a class is related to a single idea or responsibility.
  • Low cohesion means multiple unrelated methods exist within a class.
  • Fragmented functionality or methods with multiple functions within class reduces cohesion.
  • Classes with multi-concept or unrelated methods affect cohesion and often need improvements.

Coupling

  • Coupling is a measure of dependencies between classes.
  • High coupling means many dependencies exist between classes.
  • Low coupling means few dependencies.
  • Low coupling is preferred for improved class flexibility.
  • If one class changes, many other classes impacted with high coupling often require modifications as well.

Open/Closed Principle (OCP)

  • OCP states that software entities should be open for extension but closed for modification.
  • Avoid modifying existing code when adding new functionality; it should be doable by extending the class.
  • This principle reduces coupling and improves class flexibility.
  • Classes that violate this principle require modifications to add new functionality.
  • The goal is to create classes (and their elements, like methods) that, once complete and tested, should not need to be modified.
  • Modifications should be done by subclassing (inheritance).

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Related Documents

SOLID Design (CSCI 2134) PDF

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