How do you decouple abstractions and implementations in your objects?

1 Benefits of decoupling

Decoupling abstractions and implementations in your objects means reducing the dependencies and assumptions between them, so that they can be changed, replaced, or extended independently. This can have a positive impact on your OOD by improving modularity and cohesion, as well as enhancing flexibility and reusability. Additionally, decoupling abstractions and implementations can facilitate testing and maintenance by isolating the effects of changes and errors in one object from affecting other objects, as well as simplifying the verification and debugging of your code.

2 Principles of decoupling

Achieving decoupling in your OOD can be done by following a few principles and patterns, such as the abstraction principle. This states that you should program to an interface, not an implementation, meaning you should define and use abstractions of your objects as general and abstract interfaces rather than concrete and specific classes. Additionally, the dependency inversion principle states that you should depend on abstractions, not concretions. This means inverting the direction of the dependencies between your objects so that higher-level objects do not depend on lower-level objects, but rather on abstractions that the lower-level objects implement. Lastly, the bridge pattern is a structural design pattern that decouples an abstraction from its implementation by introducing a separate interface as a bridge between them. This allows varying the abstraction and implementation independently, as well as avoiding creating a large and complex class hierarchy that mixes both aspects.

3 Examples of decoupling

To illustrate the concept of decoupling in practice, let's look at some OOD scenarios where you can apply the principles and patterns discussed. For example, if you are designing a system that handles documents, you can define an abstract interface called Document, which contains the common methods and properties for all documents. Then, separate classes such as TextFile, PdfFile, or ImageFile can be created to implement the Document interface with specific details for each type of document. This allows you to use the Document interface to manipulate any document object without knowing its concrete class. Similarly, if you are creating a system that performs encryption, an abstract interface called Encryptor can be defined with common methods and properties for all encryption algorithms. Different classes such as AesEncryptor, RsaEncryptor, or DesEncryptor can then be created to implement the Encryptor interface with specific details for each type of encryption. Finally, if you are designing a system that supports databases, an abstract interface called Database can be defined with common methods and properties for all databases. Additionally, an interface called DatabaseDriver can act as a bridge between the Database interface and the specific classes that implement it, such as MysqlDatabase, OracleDatabase, or MongodbDatabase. This allows you to use the Database interface to interact with any database object without knowing its concrete class or driver.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?