Builder Design Pattern

Builder Design Pattern

Design Patterns
Creational Design Patterns

We want to produce three types of the same product P. These types are P1, P2 and P3.
P is made from four parts (components), C1, C2, C3 and C4.

The Builder Design Pattern can be employed in three easy steps:

Step 1: We develop one abstract class as Builder with four abstract methods to produce C1, C2, C3 and C4 and one method to return the product.

abstract class Builder {

   abstract ProduceC1( );
   abstract ProduceC2( );
   abstract ProduceC3( );
   abstract ProduceC4( );
   abstract GetProduct( );

}

Step 2: We develop three concrete classes inherited from the class Builder to produce P1, P2 and P3.

class BuilderForP1 : Builder {
   ...
}

class BuilderForP2 : Builder {
   ...
}

class BuilderForP3 : Builder {
   ...
}

Step 3: Then we develop a class as Director with one method to call the methods to make the components in a right order.

class Director {

   void MakeProduct(Builder builder) {
      builder.ProduceC1( );
      builder.ProduceC2( );
      builder.ProduceC3( );
      builder.ProduceC4( );  
   }

}

After the above three steps, we need to use what we developed based on the Builder Design Pattern in order to produce P1, P2 and P3. We develop a Producer class as in the following:

class Producer{
   Director director = new Director( );

   Builder builder1 = BuilderForP1( );
   director.MakeProduct(builder1)
   P1 = builder1.GetProduct( );


   Builder builder2 = BuilderForP2( );
   director.MakeProduct(builder2)
   P2 = builder2.GetProduct( );

   Builder builder3 = BuilderForP3( );
   director.MakeProduct(builder3)
   P2 = builder3.GetProduct( );

}

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