Design Patterns (Part 2)

 Page 1


CSE 403
Design Patterns (Part 2)
Page 2


CSE 403
Design Patterns (Part 2)
Outline
Introduction to design patterns
Creational patterns (constructing objects) Creational patterns (constructing objects)
Structural patterns (controlling heap layout)
Bh i l tt (ffti bjt ti )
?
?
Behavioral patterns (affecting object semantics)
?
Slide 2
Page 3


CSE 403
Design Patterns (Part 2)
Outline
Introduction to design patterns
Creational patterns (constructing objects) Creational patterns (constructing objects)
Structural patterns (controlling heap layout)
Bh i l tt (ffti bjt ti )
?
?
Behavioral patterns (affecting object semantics)
?
Slide 2
Structural patterns:  Wrappers
The wrapper translates between incompatible interfaces 
Wrappers are a thin veneer over an encapsulated class Wrappers are a thin veneer over an encapsulated class 
modify the interface
extend behavior
restrict access 
The encapsulated class does most of the work p
Pattern Functionality Interface
Adapter same different
Decorator different same Decorator different same
Proxy same same
Slide 3
Page 4


CSE 403
Design Patterns (Part 2)
Outline
Introduction to design patterns
Creational patterns (constructing objects) Creational patterns (constructing objects)
Structural patterns (controlling heap layout)
Bh i l tt (ffti bjt ti )
?
?
Behavioral patterns (affecting object semantics)
?
Slide 2
Structural patterns:  Wrappers
The wrapper translates between incompatible interfaces 
Wrappers are a thin veneer over an encapsulated class Wrappers are a thin veneer over an encapsulated class 
modify the interface
extend behavior
restrict access 
The encapsulated class does most of the work p
Pattern Functionality Interface
Adapter same different
Decorator different same Decorator different same
Proxy same same
Slide 3
Adapter
Change an interface without changing functionality
rename a method
convert units
implement a method in terms of another
Example:  angles passed in radians vs. degrees
Slide 4
Page 5


CSE 403
Design Patterns (Part 2)
Outline
Introduction to design patterns
Creational patterns (constructing objects) Creational patterns (constructing objects)
Structural patterns (controlling heap layout)
Bh i l tt (ffti bjt ti )
?
?
Behavioral patterns (affecting object semantics)
?
Slide 2
Structural patterns:  Wrappers
The wrapper translates between incompatible interfaces 
Wrappers are a thin veneer over an encapsulated class Wrappers are a thin veneer over an encapsulated class 
modify the interface
extend behavior
restrict access 
The encapsulated class does most of the work p
Pattern Functionality Interface
Adapter same different
Decorator different same Decorator different same
Proxy same same
Slide 3
Adapter
Change an interface without changing functionality
rename a method
convert units
implement a method in terms of another
Example:  angles passed in radians vs. degrees
Slide 4
Adapter example:  scaling rectangles
interface Rectangle {
// grow or shrink this by the given factor
void scale(float factor);
...
float getWidth();
float area(); 
}
class myClass {
void myMethod(Rectangle r) {
l(2) ...   r.scale(2);   ...
}
}
Could we use this class instead?
class NonScaleableRectangle {
void setWidth(float width) { ... } (){}
void setHeight(float height) { ... }
...
}
Slide 5