Refactoring Conditional Structures with Map
When working on already existing codebases, I often encounter pieces of code that look like this:
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Basically, depending on the weather, an action has to be taken. This kind of code is pretty hard to test and to maintain. The goal of this article is to refactor it using a
What is the Problem?
Using conditional structures like this might be a sign of bad design. Indeed, this code tends to grow indefinitely as new cases have to be handled and the same code has to be modified over and over. A time will come when the code will be so bloated that it will be very hard to add new behaviour. This is a violation of the Open Closed Principle which stipulates that the code should be open for extension but closed for modification: you should be able to add new behaviour to your code without modifying it.
Transform the Imperative Algorithm into Data
By analyzing this code, it becomes clear that this algorithm is no more than a
Map: for a certain weather (the key), a piece of code has to be executed (the value). A first refactoring can be done to make this conceptual
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This is a first step and the code is already much clearer. Now, the mapping between the weather and the action to perform is explicit and the
start method will not have to be modified very often. When a new case must be handled, it’s just a new entry in the
Nonetheless, this do not solve all problems. The class still has to be modified to add a new entry. To go further, the
Map can be passed as a parameter of the constructor.
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Now the only responsibility of the class is to use the mapping to perform the correct action. This mapping is now the responsibility of another class.
Note about Spring Framework
If you are using Spring Framework and the
Day class is a
@Component, you can simply inject the
Map as any other dependency.
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This refactoring is very easy to do but it can reduce the complexity of a method in a very efficient way. I think that the code should reveal intention and should not be bloated with conditional structures when it is not necessary.
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