1. OOPSLA ’04 Educator’s Symposium
Nifty Assignment: The Shape Calculator
Fix the link; fix code to close the window w/o AFrame
Demo (3)
Make the font bigger
Big buttons
Triangle factory w/ 3 points – write code, compile at runtime, load
Get students’ solutions (for each part) from last semester
Explain the assignment
Must have demo in binary with some shapes for student to work with
Makes clear of the functionality requirements
Break into 4 parts and 4 directories; grade one piece at a time
Why is it so nifty?
Eric Cheng, Dung Zung Nguyen, Mathias Ricken, Stephen Wong
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2. Niftiness Swing GUI application with the MVC pattern.
Closures via anonymous inner class
Callback architecture
Extensibility and security via factories
Dynamic nature of OO programs
Abstraction!
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3. What is a shape?
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4. What is a shape? Knows how to compute its area
Knows how to present itself visually
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5. How do we make a shape? Constructor for a rectangle:
public Rect(double width, double height)
Constructor for a circle:
public Circle(double radius) …
How to call a constructor if its parameters are unknown?
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6. Factory design pattern
Factories know how.
Can specify a clear definition of a factory: we know how to make factories.
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7. Behavioral definitions
IShapeFactory
JPanel getPropertyPanel()
IShape makeShape()
IShape
double getArea()
void paint(Graphics g, int x, int y)
Move IShape next to “what’s a shape?”
Pop up UML or code of the IShape interfrace
Move IShapeFactory as well.
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8. Behavioral definitions
Interfaces define behaviors.
A factory is a factory if it satisfies the protocols; a shape is a shape if it complies to our definition.
No need to have explicit class definitions.
Closures
Can have not only area, but also colors!
Dynamically load code at runtime
Delete this.
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9. Philosophical / Design Question
Should the shape know about, or even have the factory?
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10. GUI builders for IDEs
Rely on zero-ary public constructors for components.
Breaks encapsulation.
Violates definition of the component (is a shape a factory?)
Can possibly break the system by creating an “immature”, but perfectly legal shape.
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11. Our goal The clear distinction and separation of responsibilities
Each piece of component does what it is meant to do, and expose the appropriate amount of information
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12. Questions?
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