You have a clear responsibility for the wrong object
TL;DR: Don't be afraid to create or overload the proper objects.
- Bijection Fault.
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Find actual behavior on the real objects using the MAPPER.
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Answer the question: 'Whose responsibility is..?'
Finding responsible objects is a tough task.
If we talk to anybody outside the software world, they will tell us where we should place every responsibility.
Software engineers, on the contrary, tend to put behavior in strange places like helpers.
function add(a, b) {
return a + b;
}
// this is natural in many programming languages,
// but unnatural in real life
class GraphicEditor {
constructor() {
this.PI = 3.14;
// You shouldn't define the constant here
}
pi() {
return this.PI;
// Not this object's responsibility
}
drawCircle(radius) {
console.log("Drawing a circle with radius ${radius} " +
"and circumference " + (2 * this.pi()) * radius");
}
}class Integer {
function add(adder) {
return this + adder;
}
}
// This won't compile in many programming languages
// But it is the right place for adding responsibility
class GraphicEditor {
drawCircle(radius) {
console.log("Drawing a circle with radius " + radius +
" and circumference " + (2 * RealConstants.pi() * radius));
}
}
// PI's definition is RealConstants (or Number)'s responsibility
class RealConstants {
pi() {
return 3.14;
}
}[X] Manual
This is a semantic smell.
- Some languages force you to add protocol in some objects and not on everyone (like primitive integers, Strings, Arrays, etc.)
- Behavior
If you put the responsibilities in the proper object, you will surely find them in the same place.
Code Smells are just my opinion.
Photo by Austin Neill on Unsplash
We know an object by what it does, by what services it can provide. That is to say, we know objects by their behaviors.
David West
Software Engineering Great Quotes
This article is part of the CodeSmell Series.