Structural patterns (Adapter, Decorator, Facade) in Software Engineering - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main purpose of the Adapter pattern.

Software Engineering

The Adapter pattern is used to [1] incompatible interfaces so they can work together.

Drag options to blanks, or click blank then click option'

Aconvert

Bcombine

Cignore

Dreplace

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing Adapter with Decorator or Facade patterns.

The Adapter pattern converts one interface into another to allow incompatible interfaces to work together.

2fill in blank

medium

Complete the code to describe the Decorator pattern's function.

Software Engineering

The Decorator pattern allows behavior to be [1] to an object dynamically without affecting other objects.

Drag options to blanks, or click blank then click option'

Aremoved

Bhidden

Ccopied

Dadded

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking it removes or hides behavior instead of adding.

The Decorator pattern adds new behavior to objects dynamically, enhancing their functionality without changing their structure.

3fill in blank

hard

Fix the error in the description of the Facade pattern.

Software Engineering

The Facade pattern provides a [1] interface to a complex subsystem, making it easier to use.

Drag options to blanks, or click blank then click option'

Adetailed

Bsimplified

Ccomplex

Dhidden

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'detailed' or 'complex' which are opposite of the Facade's purpose.

The Facade pattern offers a simplified interface to a complex system, hiding its complexity from the user.

4fill in blank

hard

Fill both blanks to complete the explanation of Adapter and Decorator patterns.

Software Engineering

Adapter [1] interfaces to make incompatible classes work together, while Decorator [2] new behavior to objects.

Drag options to blanks, or click blank then click option'

Aconverts

Bremoves

Cadds

Dignores

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the roles of Adapter and Decorator.

Adapter converts interfaces to enable compatibility. Decorator adds new behavior to objects dynamically.

5fill in blank

hard

Fill all three blanks to complete the summary of the three structural patterns.

Software Engineering

Adapter [1] incompatible interfaces, Decorator [2] behavior dynamically, and Facade [3] complexity with a simple interface.

Drag options to blanks, or click blank then click option'

Aconverts

Badds

Chides

Dremoves

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing hiding complexity with removing it.

Adapter converts interfaces, Decorator adds behavior, and Facade hides complexity behind a simple interface.

Practice

1. Which structural pattern allows incompatible interfaces to work together by converting one interface into another?

easy

A. Decorator

B. Adapter

C. Facade

D. Singleton

Solution

1. Step 1: Understand the role of Adapter pattern

   The Adapter pattern converts the interface of one class into another interface clients expect, enabling incompatible interfaces to work together.

2. Step 2: Compare with other patterns

   Decorator adds features, Facade simplifies interfaces, Singleton controls instance creation. Only Adapter changes interfaces for compatibility.

3. Final Answer:

   Adapter -> Option B

4. Quick Check:

   Interface conversion = Adapter [OK]

Hint: Adapter = interface converter between incompatible parts [OK]

Common Mistakes:

• Confusing Decorator with Adapter
• Thinking Facade changes interfaces
• Mixing Singleton with structural patterns

2. Which of the following is the correct way to describe the Decorator pattern?

easy

A. It converts one interface to another.

B. It provides a simple interface to a complex system.

C. It adds new responsibilities to objects dynamically.

D. It ensures a class has only one instance.

Solution

1. Step 1: Identify the purpose of Decorator pattern

   Decorator adds new features or responsibilities to objects dynamically without changing their structure.

2. Step 2: Eliminate other options

   It provides a simple interface to a complex system. describes Facade, It converts one interface to another. describes Adapter, It ensures a class has only one instance. describes Singleton pattern.

3. Final Answer:

   It adds new responsibilities to objects dynamically. -> Option C

4. Quick Check:

   Decorator = add features dynamically [OK]

Hint: Decorator = add features without changing original object [OK]

Common Mistakes:

• Mixing Decorator with Facade
• Confusing Adapter with Decorator
• Thinking Singleton is a structural pattern

3. Consider a system where a Facade pattern is used to simplify multiple complex subsystems. What is the main benefit when a client uses the Facade?

medium

A. The client interacts with a simple interface hiding complexity.

B. The client must adapt its interface to each subsystem.

C. The client can access all subsystem details directly.

D. The client can add new features to subsystems dynamically.

Solution

1. Step 1: Understand Facade pattern role

   Facade provides a simple unified interface to a set of interfaces in a subsystem, hiding complexity from the client.

2. Step 2: Analyze options

   The client can access all subsystem details directly. is wrong because Facade hides details. The client must adapt its interface to each subsystem. describes Adapter. The client can add new features to subsystems dynamically. describes Decorator.

3. Final Answer:

   The client interacts with a simple interface hiding complexity. -> Option A

4. Quick Check:

   Facade = simple interface to complex system [OK]

Hint: Facade hides complexity behind a simple interface [OK]

Common Mistakes:

• Thinking Facade exposes all subsystem details
• Confusing Facade with Adapter or Decorator
• Assuming Facade adds features dynamically

4. A developer tries to use an Adapter pattern but the client code still fails due to interface mismatch. What is the most likely error?

medium

A. The client code is using the correct interface.

B. The Decorator pattern was used instead of Adapter.

C. The Facade pattern was applied to simplify the interface.

D. The Adapter does not implement the target interface correctly.

Solution

1. Step 1: Identify Adapter pattern requirement

   Adapter must implement the target interface expected by the client to convert calls properly.

2. Step 2: Analyze failure cause

   If the client still fails, likely the Adapter does not correctly implement or map the target interface methods.

3. Final Answer:

   The Adapter does not implement the target interface correctly. -> Option D

4. Quick Check:

   Adapter interface mismatch = implementation error [OK]

Hint: Adapter must match target interface exactly [OK]

Common Mistakes:

• Confusing Decorator or Facade with Adapter errors
• Assuming client code is always correct
• Ignoring interface method signatures

5. You have a legacy payment system with a complex API. You want to provide a simple interface for new clients and also add logging features without changing the legacy code. Which combination of structural patterns should you use?

hard

A. Facade to simplify interface and Decorator to add logging

B. Decorator to simplify interface and Adapter to add logging

C. Adapter to add logging and Facade to simplify interface

D. Adapter to simplify interface and Decorator to add logging

Solution

1. Step 1: Identify pattern for simplifying complex API

   Facade provides a simple interface to a complex system, ideal for the legacy payment system.

2. Step 2: Identify pattern for adding features without changing code

   Decorator adds new responsibilities like logging dynamically without modifying original code.

3. Step 3: Combine patterns logically

   Use Facade to simplify the interface for clients, then wrap with Decorator to add logging features.

4. Final Answer:

   Facade to simplify interface and Decorator to add logging -> Option A

5. Quick Check:

   Simplify = Facade, Add features = Decorator [OK]

Hint: Facade simplifies, Decorator adds features without code change [OK]

Common Mistakes:

• Using Adapter to simplify interface instead of Facade
• Confusing roles of Adapter and Decorator
• Trying to add logging via Adapter