How can you apply the principle of least knowledge using design patterns?

1 Facade Pattern

The facade pattern is a structural pattern that provides a simplified interface to a complex subsystem or a set of classes. It hides the details and interactions of the subsystem from the clients, and only exposes the essential functionality. The facade acts as a mediator between the clients and the subsystem, and reduces the coupling between them. The clients only need to know about the facade, and not about the internal structure or behavior of the subsystem. The facade pattern follows the principle of least knowledge by limiting the communication between the clients and the subsystem to a single object.

2 Proxy Pattern

The proxy pattern is a structural pattern that provides a surrogate or placeholder for another object. It controls the access to the original object, and can perform additional operations before or after the access. The proxy can be used for various purposes, such as caching, logging, validation, security, or remote access. The proxy pattern follows the principle of least knowledge by decoupling the clients from the original object, and only exposing the interface that is relevant to the clients. The clients do not need to know about the implementation details or the location of the original object, and only interact with the proxy.

3 Observer Pattern

The observer pattern is a behavioral pattern that defines a one-to-many dependency between objects. It allows an object, called the subject, to notify its observers, or subscribers, when its state changes. The observers register themselves with the subject, and can update their behavior accordingly. The observer pattern follows the principle of least knowledge by allowing the subject and the observers to be loosely coupled. The subject does not need to know about the specific classes or methods of the observers, and only communicates with them through a common interface. The observers do not need to know about the internal state or logic of the subject, and only receive the notifications that they are interested in.

4 Strategy Pattern

The strategy pattern is a behavioral pattern that defines a family of algorithms, and lets an object, called the context, choose one of them at runtime. It encapsulates the algorithms in separate classes, called strategies, and makes them interchangeable. The strategy pattern follows the principle of least knowledge by isolating the algorithms from the context, and only exposing a common interface. The context does not need to know about the implementation details or the differences between the strategies, and only interacts with them through the interface. The strategies do not need to know about the context or its state, and only perform their specific tasks.

5 Command Pattern

The command pattern is a behavioral pattern that encapsulates a request or an action as an object, called a command. It allows an object, called the invoker, to execute the command without knowing the details or the receiver of the request. The command pattern follows the principle of least knowledge by decoupling the invoker from the receiver, and only exposing a common interface. The invoker does not need to know about the receiver or its methods, and only invokes the command. The command does not need to know about the invoker or its state, and only executes the request on the receiver.

6 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?