Go Patterns

How to Implement Mediator Pattern in Go

Behavioral Design Patterns in Go

Mediator Pattern in Go

Sometimes we have a bunch of objects that need to interact with each other. A number of objects can be large and their interactions can have complex logic.

Mediator pattern helps to organize such cases.

• Mediator lets keep loose coupling and don’t let objects have direct communication.
• Mediator keeps the interaction logic and allows to change it independently.

Let’s look for an example!

A chat

For example, we have a bunch of Users and they want to interact with each other.

• A User can send a message to another User.
• A User can send a message to all Users.
• Some Users can be unavailable for messaging.

So we introduce a Chat object that keeps this logic and organizes communication.

Gophers chat

User type

Firstly, we will introduce a User type. It will have a Name and store Messages.

User type

Chat type

Then we need a Chat type. It will have a method to Add a User and keep information about Users in the Chat. This is our Mediator.

Chat type

Interaction logic

Now, let’s extend our Chat with interaction logic.

• Say(to User, msg string) - sends a message to the specific User and handles an error if the User is not in the Chat.
• SayAll(msg string) - sends a message to the all available Users.

Interaction logic

Usage Example

Now, we gather all pieces together to see how it works.

Main function

Conclusion

Mediator pattern is a good example of encapsulation logic into separate entity. It’s a complement to the Observer pattern. In real world applications though the logic can grow a lot, and turn this into God object antipattern.

Happy coding!

Code examples can be found in my GitHub repo pavel-fokin/go-patterns.

More reading

If you like this article you can be interested in the following.

Why Do Programming Languages Have Types?

How to Implement Memento Pattern in Go

Originally published at https://pavelfokin.dev.