How to merge multiple hashes?

Question

Right now, I'm merging two hashes like this:

department_hash  = self.parse_department html
super_saver_hash = self.parse_super_saver html

final_hash = department_hash.merge(super_saver_hash)

Output:

{:department=>{"Pet Supplies"=>{"Birds"=>16281, "Cats"=>245512, "Dogs"=>513926, "Fish & Aquatic Pets"=>46811, "Horses"=>14805, "Insects"=>364, "Reptiles & Amphibians"=>5816, "Small Animals"=>19769}}, :super_saver=>{"Free Super Saver Shipping"=>126649}}

But now I want to merge more in the future. For example:

department_hash  = self.parse_department html
super_saver_hash = self.parse_super_saver html
categories_hash  = self.parse_categories html

How to merge multiple hashes?

Solution 1

You can do below way using Enumerable#inject:

h = {}
arr = [{:a=>"b"},{"c" => 2},{:a=>4,"c"=>"Hi"}]
arr.inject(h,:update)
# => {:a=>4, "c"=>"Hi"}
arr.inject(:update)
# => {:a=>4, "c"=>"Hi"}

Solution 2

How about:

[department_hash, super_saver_hash, categories_hash].reduce &:merge

Solution 3

You can just call merge again:

h1 = {foo: :bar}
h2 = {baz: :qux}
h3 = {quux: :garply}

h1.merge(h2).merge(h3)
#=> {:foo=>:bar, :baz=>:qux, :quux=>:garply}

Comments

[Arup Rakshit]

why & ? [department_hash, super_saver_hash, categories_hash].reduce(:merge) is fine...

[pguardiario]

That's just my preference. I think the & informs something and is worthwhile.

[Patrick Oscity]

@Babai because this style is consistent with e.g. Enumerable#map which requires a proc.

[bigtunacan]

I think the point is how would it be possible to do this with a single call. h1.merge(h2, h3) Obviously this does not actually work, but such behavior could be useful.

[user1735921]

this is what I was looking for