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Questions and Answers
What is the primary responsibility of the Model in the MVC architecture?
What is the primary responsibility of the Model in the MVC architecture?
In the MVC architecture, what action does the Controller perform?
In the MVC architecture, what action does the Controller perform?
What is a key benefit of utilizing MVC architecture in software development?
What is a key benefit of utilizing MVC architecture in software development?
Which of the following best describes the interaction cycle in MVC?
Which of the following best describes the interaction cycle in MVC?
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How does the View in the MVC architecture know when to update its display?
How does the View in the MVC architecture know when to update its display?
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What programming paradigm does MVC combine well with for building interactive applications?
What programming paradigm does MVC combine well with for building interactive applications?
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Which statement regarding the history of MVC is correct?
Which statement regarding the history of MVC is correct?
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What does the View do in the MVC structure?
What does the View do in the MVC structure?
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What must be called in the model after a data change occurs to indicate that a change has happened?
What must be called in the model after a data change occurs to indicate that a change has happened?
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What happens when notifyObservers() is called without any arguments?
What happens when notifyObservers() is called without any arguments?
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Which method allows the Model to send data to the Observers when notifying them?
Which method allows the Model to send data to the Observers when notifying them?
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Which component is primarily responsible for responding to user interactions in the MVC architecture?
Which component is primarily responsible for responding to user interactions in the MVC architecture?
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What is a benefit of using the Observer pattern in the MVC architecture?
What is a benefit of using the Observer pattern in the MVC architecture?
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How does the View request data from the Model in a pull architecture?
How does the View request data from the Model in a pull architecture?
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What is an example of how multiple Views can be utilized within the MVC with Observer pattern?
What is an example of how multiple Views can be utilized within the MVC with Observer pattern?
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What role does the Observable class play in the MVC architecture?
What role does the Observable class play in the MVC architecture?
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Why might a View choose to use push updates over pull?
Why might a View choose to use push updates over pull?
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What does the Controller do when an event, like a button click, occurs?
What does the Controller do when an event, like a button click, occurs?
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Study Notes
CMPT 270: Developing Object Oriented Systems - Model-View-Controller Architecture
- The course covers object-oriented system development using the Model-View-Controller (MVC) architecture.
- Learning objectives include understanding MVC architecture, differentiating it from three-layer architecture, and implementing MVC using the Observer pattern.
Model-View-Controller Design Pattern
- Model: Holds and manipulates data, performs business logic, notifies the View when data changes.
- View: Takes user input, presents and visualizes data.
- Controller: Receives user input, converts it into messages for the Model.
MVC - Interaction Cycle
- The MVC architecture mirrors the human interaction cycle with an interactive application.
- The flow is: Real World → User → View → Controller → Model → Program/System
Benefits of MVC
- Provides a recognizable structure to applications.
- Offers separation of concerns, which promotes code reusability.
Adoption of MVC
- MVC, originally introduced in SmallTalk in the 1970s, is language- and platform-agnostic.
- It's commonly used to develop user interfaces by dividing related program logic into three interconnected elements.
- Frequently used in games and visually interactive systems (like drawing applications).
Exercise 1: A Simple MVC System
- Create classes for the Model, View, and Controller.
- Develop a simple incrementing calculator program using MVC.
MVC with Observer Pattern
- The View implements the Observer interface.
- The Model's
update()
method is called when its data changes. - The Model tells the View its data has changed using
notifyObservers()
.
Model - Observable
- The Model should inherit from the Observable class in Java.
- This lets the Model have Observers added to it.
- The
addObserver()
method is inherited from the Observable class. -
model.addObserver(view)
is typically placed after creating the Model and View to enable the View to receive notifications when the Model changes.
In the Model
- After making a data change, use
setChanged()
to signal the data alteration. -
notifyObservers()
tells all observers the model has updated. - This triggers the
update()
method in the observers.
Updating the View
- The View, after being notified of an update, can either fetch model data using accessor methods (pull) or receive updated data directly (push).
- When employing pull, the View must access the Model (typically as an instance variable).
Push Updates
- Use
notifyObservers(Object arg)
to send specific data to observers when the model changes. This is a push update method. - If push updates are used, the View does not need direct access to the model.
Observers
- A model can have multiple observers.
- All observers are notified when the model changes.
- The Model has little knowledge of its observers; this promotes code reuse and reduces coupling.
Controller
- The controller handles user interactions and communicates to the Model.
- If a user action (like a button click) occurs, the controller tells the Model to change.
- This triggers notifications to observers (like the View), that data may have changed.
Example 2: MVC with Observer
- Refactor the simple MVC system to integrate the Observer pattern.
Exercise 3: MVC with Multiple Views
- MVC with the Observer pattern promotes loose coupling between the Model and View.
- Multiple views can receive updates from the Model and display the model in different ways (e.g., video game, minimap).
- Add a second view and include it in the Model's observers.
Summary
- MVC is commonly used to build interactive systems.
- The Observer pattern simplifies updating the view when the model changes.
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Description
Test your knowledge on the Model-View-Controller (MVC) architecture in object-oriented systems. This quiz covers the fundamental concepts, interaction cycles, and benefits of MVC in system development. Perfect for students of CMPT 270.