Skip to content

Instantly share code, notes, and snippets.

@thinkerbot thinkerbot/README.md
Last active Aug 29, 2015

Embed
What would you like to do?
Clean merge

One way to merge nested configs cleanly:

  • flatten key paths
  • merge

This approach overcomes the issue of performing a deep merge when an overlay has the ability to specify a value or a hash. This does not deal with merging array values.

Here is the issue:

c1 = {"a" => 1}
c2 = {"a" => 2}
c3 = {"a" => {"b" => 1}}
c4 = {"a" => {"b" => 2}}

deep_merge(c1, c2)
# => {"a" => 2}

deep_merge(c3, c4)
# => {"a" => {"b" => 2}}

deep_merge(c1, c4)
# => {"a" => 1}             # preserve value (?)
# => {"a" => {"b" => 2}}    # preserve hash (?)

Here is the a solution:

flat_merge(c1, c2)
# => {"a" => 2}

flat_merge(c3, c4)
# => {"a" => {"b" => 2}}

flat_merge(c1, c4)
# => {"a" => 1, "a.b" => 2}

Note that in a flat merge a flat key is equivalent to the key path in the nested structure:

c1 = {"a.b" => 1}
c2 = {"a" => {"b" => 2}}
flat_merge(c1, c2)
# => {"a.b" => 2}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.