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写不写注释? Elixir 给出另外一个答案

# To be or not to be #

我们也许曾经在写注释与不写之间摇晃不已, 不写是因为代码容易变化而注释往往被忽略掉了,这时注释反而有害; 但又因为就算一个有意义的名字 也难以信达雅的传递程序的意义. Elixir 给出了它的答案.

But the problem with comments is that they just don’t get maintained. The code changes, the comment gets stale, and it becomes useless. Fortunately, ExUnit has doctest, a tool that extracts the iex sessions from your code’s @doc strings, runs it, and checks that the output agrees with the comment.

Elixir 提倡写注释, 写注释时要按照基本法, 给出该函数的使用例子:

@doc """
Return a format string that hard codes the widths of a set of columns. We put `" | "` between each column.
## Example
    iex> widths = [5,6,99]
    iex> Issues.TableFormatter.format_for(widths)
    "~-5s | ~-6s | ~-99s~n"
def format_for(column_widths) do
map_join(column_widths, " | ", fn width -> "~-#{width}s" end) <> "~n"

而 Elixir 则提供了 doctest 工具, 自动执行你在里面写的用例, doc 的测试还会集成到整个项目的测试中. 所以通过这个保证, 大大减少了注释没有更新的情况. 结合优雅的命名, 应该是对这个问题的银弹. 当然, 没有银弹.