I often times find myself in situations where I need to rename one or more
keys in a Map, when for instance, converting from Strings to Atoms:
new_map = %{
foo: Map.fetch!(old_map, "foo"),
bar: Map.fetch!(old_map, "bar"),
...
}
or otherwise taking a Map from one part of the system and renaming keys to
make it work in another part of the system:
new_map = %{
user_id: post.author_id,
content: post.body,
...
}
With a Map.rename_key/3 function, we could instead write:
new_map =
old_map
|> Map.rename_key("foo", :foo)
|> Map.rename_key("bar", :bar)
...
or:
new_map =
post
|> Map.rename_key(:user_id, :author_id)
|> Map.rename_key(:body, :content)
...
In the situation that you're performing a bulk update of key names (as
seems to be implied above), Map.rename_keys/3 makes more sense:
new_map = Map.rename_keys(old_map, %{"foo" => :foo, "bar" => :bar, ...})
or:
new_map = Map.rename_keys(post, %{author_id: :user_id, body: :content, ...})
With the Map.rename_key[s]/3 functions, the intent is very explicit, and
induces less cognitive load to understand.
Renaming Map keys is a situation I run into at least monthly, and I do
wonder whether the rest of the community has this problem as well so as to
make it a worthwhile addition.
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