	CS 535 Object-Oriented Programming & Design Spring Semester, 1999 Builder
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Contents of Doc 16, Builder

Reference

Builder

Reference

Design Patterns: Elements of Reusable Object-Oriented Software, Gamma, Helm, Johnson, Vlissides, Addison Wesley, 1995, pp. 97-105


Doc 16, Builder Slide # 2

Builder

Intent
Separate the construction of a complex object from its representation so that the same construction process can create different representations

Applicability
Use the Builder pattern when

the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled

the construction process must allow different representations for the object that's constructed

the complex object needs to be constructed step by step


Doc 16, Builder Slide # 3

Sample Builder Interface

class MazeBuilder {
   void buildMaze() { }
   void buildRoom( roomData ) { }
   void buildDoor( doorData ) { }
   void buildCorridor( corridorData ) { }
   // Call this when maze is complete
   Maze getMaze() { }
}
The builder know how to build mazes step by step
The builder does not know what maze you wish to build
A separate object, a director, knows the steps needed to construct a particular maze, but does not know how to build mazes or room, etc.
Doc 16, Builder Slide # 4

Collaborations
The client creates the Director object and configures it with the desired Builder object

Director notifies the builder whenever a part of the product should be built

Builder handles requests from the director and adds parts to the product

The client retrieves the product from the builder


Doc 16, Builder Slide # 5

Consequences
It lets you vary a product's internal representation

It isolates code for construction and representation

It gives you finer control over the construction process

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1999 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
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