Midterm2024 Flashcards
What is the intent of the Flyweight pattern?
Use sharing to support large numbers of fine-grained objects efficiently.
What type of pattern classification is the Flyweight pattern?
Object Structural
What is a Flyweight?
A shared object that can be used in multiple contexts simultaneously
What type of state is stored in the Flyweight?
Intrinsic
What type of state is stored with the Flyweight’s context?
Extrinsic
What 4 things must be true to use the Flyweight pattern?
- App uses a large number of objects making storage costs high
- Most object state can be made extrinsic
- Removing extrinsic state allows many groups of objects to be replaced by few shared objects
- The application doesn’t depend on object identity (identity tests will return true)
What are the 5 participants of the Flyweight pattern?
- Flyweight
- ConcreteFlyweight
- UnsharedConcreteFlyweight
- FlyweightFactory
- Client
What 2 issues need to be considered when implementing the Flyweight pattern?
- Removing extrinsic state
- Managing shared objects
What type of pattern classification is the Strategy pattern?
Object Behavioural
What is the intent of the Strategy pattern?
Define a family of algorithms and make them interchangeable.
What else is the Strategy pattern known as?
Policy
What are the 3 participants of the Strategy pattern?
- Strategy
- ConcreteStrategy
- Context
How do the Context and the Strategy share data?
Context either passes all required data to the strategy or passes itself to the strategy
What participant does the Client interact with in a Strategy pattern?
After creating a ConcreteStrategy and passing it to the Context, Clients interact with Context exclusively.
What are 2 alternatives to using the Strategy pattern?
- Subclassing
- Conditional Statements
What type of pattern classification is the Iterator pattern?
Object Behavioural
What is the intent of the Iterator pattern?
Provide a way to access the elements of an aggregate object sequentially without exposing underlying representation
What is another name for the Iterator pattern?
Cursor
What is the key idea behind the Iterator pattern?
Take responsibility for access and traversal out of the list object and into an iterator object
What are the 4 participants of the Iterator pattern?
- Iterator
- ConcreteIterator
- Aggregate
- ConcreteAggregate
What is it called when a client controls the iteration?
External Iterator
What is it called when the aggregate defines the traversal algorithm of an Iterator and uses the iterator to store state of iteration?
Cursor
What type of pattern classification is the Prototype pattern?
Object Creational
What is the intent of the Prototype pattern?
Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype
What are the 3 participants of the Prototype pattern?
- Prototype
- ConcretePrototype
- Client
What are the 3 scenarios where the Prototype pattern should be used?
- Classes you need to instantiate are specified at run-time
- Want to avoid building a ton of factories
- Instances of a class only have a few different combinations of state
What type of pattern classification is the Template pattern?
Class Behavioural
What is the intent of the Template pattern?
Define the skeleton of an algorithm and deferring some steps to subclasses
What is a template method?
Defines an algorithm in terms of abstract operations that subclasses override to provide concrete behaviour
What are the 2 participants in the Template pattern?
- AbstractClass
- ConcreteClass
What operations can optionally be overridden in the Template pattern?
Hooks
Which operations must be overridden in the Template pattern?
Abstract
The Template pattern is the Class Behavioural version of what other pattern?
Strategy
What is meant by “the Hollywood principle”?
Inverted control structure where the parent class calls operations on the subclass.
“Don’t call us, we’ll call you”
What pattern is considered a form of the Template method?
Factory Method
What 2 criteria are patterns classified by?
- Purpose
- Scope
What are the 3 purpose sub-categories for pattern classification?
- Creational
- Structural
- Behavioural
What are the 2 scope sub-categories for pattern classification?
- Class
- Object
