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Cover image for Code Smell 143 - Data Clumps
Maxi Contieri
Maxi Contieri

Posted on • Originally published at maximilianocontieri.com

Code Smell 143 - Data Clumps

Some objects are always together. Why don't we split them?

TL;DR: Make cohesive primitive objects travel together

Problems

  • Bad Cohesion

  • Duplicated Code

  • Validation Complexity

  • Readability

  • Maintainability

Solutions

  1. Extract Class

  2. Find small objects

Context

This smell is friends with primitive obsession.

If two or more primitive objects are glued together, with business logic repeated and rules between them, we need to find the existing concept on the bijection.

Sample Code

Wrong

public class DinnerTable
{
    public DinnerTable(Person guest, DateTime from, DateTime to)
    {
        Guest = guest; 
        From = from;
        To = to;
    }
    private Person Guest;
    private DateTime From; 
    private DateTime To;
}
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Right

public class TimeInterval
{
    public TimeInterval(DateTime from, DateTime tol)
    {
        // We shoud validate From < To
        From = from;
        To = to;
    }
}

public DinnerTable(Person guest, DateTime from, DateTime to)
{    
    Guest = guest;
    Interval = new TimeInterval(from, to);
}
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Detection

[X] Semi-Automatic

Detection based on cohesion patterns is available o a few linters.

Tags

  • Cohesion

Conclusion

Group behavior in the right place and hid the primitive data.

Relations

More Info

Credits

Photo by Dynamic Wang on Unsplash


The heart of the software is its ability to solve domain-related problems for its user. All other features, vital though they may be, support this basic purpose.

Eric Evans


This article is part of the CodeSmell Series.

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