Making long chains generate coupling and ripple effect. Any chain change breaks the code.

TL;DR: Just sent messages to your acquaintances.

Problems

• Coupling

• Break encapsulation

Solutions

• Create intermediate methods.
• Think about Law of Demeter.
• Create higher level messages.

Sample Code

Wrong

class Dog {
   constructor(feet) {
     this.feet = feet;    
  }
  getFeet() {    
    return this.feet;
  }  
}

class Foot {
  move(){    
    //..
  }
}

feet = [new Foot(), new Foot(), new Foot(), new Foot()];
dog = new Dog(feet);

for (var foot of dog.getFeet()) {
  foot.move(); 
}

Right

class Dog {
   constructor(feet) {
     this.feet = feet;    
  }
  walk(){
    for (var foot of this.feet) {
      foot.move(); 
    }
  }
}

class Foot {
  move(){    
    //..
  }
}

feet = [new Foot(), new Foot(), new Foot(), new Foot()];
dog = new Dog(feet);
dog.walk();

Detection

Automatic detection is possible using parsing trees.

Also Known as

• Message Chains

• Law of Demeter

Relations

More Info

• Refactoring Guru

Tags

• Declarative

• Encapsulation

Conclusion

Avoid successive message calls. Try to hide the intermediate collaborations and create new protocols.

Credits

Photo by Chewy on Unsplash

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This article is part of the CodeSmell Series.

Last update: 2021/06/10