Small changes yield unexpected problems.

TL;DR: If small changes have big impact, you need to decouple your system.

Problems

• Coupling

Solutions

1. Decouple.
2. Cover with tests.
3. Refactor and isolate what is changing.
4. Depend on interfaces.

Examples

• Legacy Systems

Sample Code

Wrong

class Time {
   constructor(hour, minute, seconds) {
     this.hour = hour;    
     this.minute = minute;  
     this.seconds = seconds;  
  }
    now(){
      //call operating system
    }  
}

//Adding a TimeZone will have a big Ripple Effect
//Changing now() to consider timezine will also bring the effect

Right

class Time {
   constructor(hour, minute, seconds, timezone) {
     this.hour = hour;    
     this.minute = minute;  
     this.seconds = seconds;  
     this.timezone = timezone;  
  }  
  //Removed now() since is invalid without context
}

class RelativeClock {
   constructor(timezone){
     this.timezone = timezone;
   }
   now(timezone){
     var localSystemTime = this.localSystemTime();
     var localSystemTimezone = this.localSystemTimezone();
     //Do some math translating timezones
     //
     return new Time(..., timezone);     
   }  
}

Detection

• It is not easy to detect problems before they happen. Mutation Testing and root cause analysis of single points of failures may help.

Tags

• Legacy

Conclusion

There are multiple strategies to deal with Legacy and coupled systems. We should deal with this problem before it explodes under our eyes.

Relations

• Code Smell 08 - Long Chains Of Collaborations

More info

• How to Decouple a Legacy System

Credits

Photo by Jack Tindall on Unsplash

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Architecture is the tension between coupling and cohesion.

Neal Ford

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This article is part of the CodeSmell Series.

Last update: 2021/06/24