Chapter 18 Code Should be Obvious

Obscurity is one of the two main causes of complexity described in Section 2.3. Obscurity occurs when important information about a system is not obvious to new developers. The solution to the obscurity problem is to write code in a way that makes it obvious; this chapter discusses some of the factors that make code more or less obvious.

If code is obvious, it means that someone can read the code quickly, without much thought, and their first guesses about the behavior or meaning of the code will be correct. If code is obvious, a reader doesn’t need to spend much time or effort to gather all the information they need to work with the code. If code is not obvious, then a reader must expend a lot of time and energy to understand it. Not only does this reduce their efficiency, but it also increases the likelihood of misunderstanding and bugs. Obvious code needs fewer comments than nonobvious code.

“Obvious” is in the mind of the reader: it’s easier to notice that someone else’s code is nonobvious than to see problems with your own code. Thus, the best way to determine the obviousness of code is through code reviews. If someone reading your code says it’s not obvious, then it’s not obvious, no matter how clear it may seem to you. By trying to understand what made the code nonobvious, you will learn how to write better code in the future.

18.1 Things that make code more obvious

18.2 Things that make code less obvious

18.3 Conclusion

Another way of thinking about obviousness is in terms of information. If code is nonobvious, that usually means there is important information about the code that the reader does not have: in the RaftClient example, the reader might not know that the RaftClient constructor created new threads; in the Pair example, the reader might not know that result.getKey() returns the number of the current term.

To make code obvious, you must ensure that readers always have the information they need to understand it. You can do this in three ways. The best way is to reduce the amount of information that is needed, using design techniques such as abstraction and eliminating special cases. Second, you can take advantage of information that readers have already acquired in other contexts (for example, by following conventions and conforming to expectations) so readers don’t have to learn new information for your code. Third, you can present the important information to them in the code, using techniques such as good names and strategic comments.