Many programming languages (including Ruby) ship with a built-in
merge function for combining 2 maps (hashes). Usually we'll follow
straightforward "last-one wins" semantics -- if 2 merged hashes contain
the same key then the second one will win. For example:
{:a => 1}.merge({:a => 2})
=> {:a=>2}However sometimes we'd like to perform a merge using a customized process for combining overlapping values: merge 2 hashes by summing, concatenating, or subtracting the values of matching keys, etc.
Let's implement a function to do this. Define your own method merge_with
which takes 3 arguments:
- A hash
- Another hash
- A 2-argument block specifying the process that should be used to combine value of any matching keys.
For example:
merge_with({:a => 1}, {:a => 2, :b => 1}) do |a,b|
a + b
end
=> {:a => 3, :b => 1}