Code Smell 67 - Middle Man

Remove the Intermediators

4 May, 2023

Contributors

Maxi Contieri

@mcsee

TL;DR: Remove the Intermediators

Let's break Demeter's Law.

Problems

Unnecessary Indirection
Empty Classes
Readability

Solutions

Remove Middle man.

Sample Code

Wrong

public class Client {
    Address address;
    public ZipCode zipCode() {
        return address.zipCode();
    }
}

public class Address {
    private ZipCode zipCode;

    public ZipCode zipCode() {
        return new ZipCode('CA90210');
    }
}

public class Application {   
   ZipCode zipCode = client.zipCode();
}

Right

public class Client {
    Address address;
    // client now has to expose its address
    public address() {
        return address;
    }
}

public class Address {
    private ZipCode zipCode;

    public ZipCode zipCode() {
        return new ZipCode('CA90210');
    }
}

public class Application {   
   ZipCode zipCode = client.address().zipCode();
}

Detection

Same as its opposite smell, We can detect this small using parsing trees.

Conclusion

This is exactly the opposite to Message Chain. We make explicit the message chain.

Relations

Code Smell 08 - Long Chains Of Collaborations

Code Smell 114 - Empty Class

More Info

(Refactoring Guru)[https://refactoring.guru/smells/middle-man]

(Refactoring.com)[https://refactoring.com/catalog/removeMiddleMan.html]

(C2 Wiki)[https://wiki.c2.com/?MiddleMan]

(JetBrains)[https://www.jetbrains.com/help/idea/remove-middleman.html#remove_middleman_example]

(Wikipedia)[https://en.wikipedia.org/wiki/Law_of_Demeter]

Credits

Photo by Dan Counsell on Unsplash

Whenever I have to think to understand what the code is doing, I ask myself if I can refactor the code to make that understanding more immediately apparent.

Martin Fowler

Software Engineering Great Quotes

This article is part of the CodeSmell Series.

How to Find the Stinky Parts of your Code