Couplers

"Couplers" are the code smells that represent excessive coupling between classes. Coupling is a measure of how closely connected two modules are. If they are too tightly coupled, changing one requires changing the other.

Think of your code like a stereo system. In a good system, you can unplug the speakers and plug in new ones because the connection (the interface) is standard and simple. In a bad system ("Coupled"), the speaker wires are soldered directly onto the motherboard. You can't upgrade the speakers without buying a new amplifier.

When classes are too intimate, know too much about each other, or envy each other's data, your system becomes rigid and fragile.

Smell List

Here are the classic smells in this category:

Feature Envy

A method seems more interested in a class other than the one it actually is in. It envies the data of another class.

Inappropriate Intimacy

Classes spend too much time together, accessing each other's private parts. A subclass knowing too much about its parent is also a form of this.

Message Chains

The classic a.getB().getC().doSomething(). The client is coupled to the structure of the navigation.

Middle Man

The opposite of Message Chains. A class does too much simple delegation, acting as a wrapper that adds no value.

Indecent Exposure

Classes or methods that are public when they ought to be private. It invites coupling where there shouldn't be any.

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In this section, we will look at how to untangle these relationships and restore healthy boundaries to your objects.