Bridge method is a Structural Design Pattern which allows us to separate the Implementation Specific Abstractions and Implementation Independent Abstractions from each other and can be developed considering as the single entities.
Bridge Method is always considered as one of the best methods to organize the class hierarchy.
Elements of Bridge Design Pattern
- Abstraction : It is the core of the Bridge Design Pattern and it provides the reference to the implementer.
- Refined Abstraction : It extends the abstarction to the new level where it takes the finer details one level above and hides the finer element from the implementors.
- Implementer: It defines the interface for implementation classes. This interface does not need to correspond directly to the abstraction interface and can be very different.
- Concrete Implemntation: Through the concrete implementation, it implements the above implementer.
Problem without using Bridge Method
Consider the following class Cuboid which has three attributes named as length, breadth, and height and three methods named as ProducewithAPI1(), ProduceWithAPI2() and expand().
Out of these, producing methods are implementation-specific as we have two production APIs and one method i.e., expand() method is implementation-independent.
Till now we have only two implementation-specific methods and one implementation-independent method but when the quantity will rise (of course in a large-scale project) things will become messy for the developers to handle.
Note: Following code is written without using Bridge method.
Solution using Bridge method
Now let’s look at the solution for the above problem. Bridge Method is one of the best solutions for such kind of problems. Our main purpose is to separate out the codes of implementation specific abstractions and implementation independent abstractions.
Note: Following Code is written using Bridge Method
UML Diagram of Bridge Method
Following is the UML diagram for Bridge Method
- Single Responsibility Principle: Bridge method clearly follows the Single Responsibility principle as it decouple an abstraction from its implementation so that the two can vary independently.
- Open/Closed Principle: It does not violate the Open/Closed principle because at any time we can introduce the new abstractions and implementations independently form each other
- Platform independent feature: Bridge Method can be easily used for implementing the platform independent features.
- Complexity: Our code might become complexive after applying Bridge method because we are introding new abstarction classes and interfaces.
- Double Indirection: Bridge method might have slight negative impact on the preformance because the abstraction needs to pass messages along with the implementator for the operation to get executed.
- Interfaces with only single implementation: If we have only limited interfaces, then it doesn’t sweat a breath but if you have an exploded set of interfaces with minimal or only one implementation it becomes hard to manage
- Run-time Binding: Generally Bridge method is used to provide the run-time binding of the implementation, here run-time binding refers to that we can call a method at run-time instead of compile-time.
- Mapping classes: Bridge method is used to map the orthogonal class hierarchies
- UI Environment: A real life application of Bridge method is used in the definition of shapes in an UI Environment
Further read: Bridge Method in Java
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