Merging multiple hashes as single hash

rubyonrails-talk
1

Hi All,

I'm having unknown number of hashes. How to merge all those hashes into single hash?

Thanks, Buvana

2

Priya Buvan wrote in post #967340:

Hi All,

I'm having unknown number of hashes. How to merge all those hashes into single hash?

Think about the semantics here! What happens if the same key appears in all the hashes? Which value takes priority?

You can use inject to merge the hashes, but you probably won't get the desired result.

Thanks, Buvana

Best,

3

use "merge"... Class: Hash (Ruby 3.1.2)

When you say you have "unknown number", are they in an array? if so, iterate it an merge them...

4

@Michael: yes its in array..

@Marnen: If there is more than one key with same name, obviously it'll be override. This is fine.

Anyway i'm trying to fetch the result separately. I'll reply with latest updated soon.

Thanks, Buvana

5

array_of_hashes = [{:first => 1, :second => 2}, {:first => 10, :third => 3}]

Hash[*array_of_hashes.collect{|hash| hash.collect{|key,value| [key,value].flatten}.flatten}.flatten] => {:first=>10, :second=>2, :third=>3}

6

array_of_hashes = [{:first => 1, :second => 2}, {:first => 10, :third => 3}]

Hash[*array_of_hashes.collect{|hash| hash.collect{|key,value| [key,value].flatten}.flatten}.flatten] => {:first=>10, :second=>2, :third=>3}

Simpler, but same idea.

Hash[*array_of_hashes.map{|_|_.to_a}.flatten]

=> {:second=>2, :third=>3, :first=>10}

-Rob

Rob Biedenharn Rob@AgileConsultingLLC.com http://AgileConsultingLLC.com/ rab@GaslightSoftware.com http://GaslightSoftware.com/

7

You can use inject to merge the hashes, but you probably won't get the desired result.

Actually, looks like you get the desired result

a = [{:first => 1, :second => 2}, {:first => 10, :third => 3}] a.inject(:merge)

8

In case you need something more smart in the future to deal with same keys in hashes:

http://rubyworks.github.com/facets/doc/api/core/Hash.html#method-i-weave

Robert Pankowecki