Merging multiple hashes as single hash

[Priya Buvan]

Hi All,

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

Thanks,
Buvana

--
Posted via http://www.ruby-forum.com/.

[Marnen Laibow-Koser]

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,
-- 
Marnen Laibow-Koser
http://www.marnen.org
mar...@marnen.org

Sent from my iPhone

[Michael Pavling]

On 9 December 2010 06:09, Priya Buvan <li...@ruby-forum.com> wrote:
> I'm having unknown number of hashes. How to merge all those hashes into
> single hash?

use "merge"... http://ruby-doc.org/core/classes/Hash.html#M002880

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

[Priya Buvan]

@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.

[Vladimir Rybas]

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}

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[Rob Biedenharn]

On Dec 9, 2010, at 7:09 AM, Vladimir Rybas wrote:

> 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.

irb> Hash[*array_of_hashes.map{|_|_.to_a}.flatten]
=> {:second=>2, :third=>3, :first=>10}

-Rob

Rob Biedenharn
R...@AgileConsultingLLC.com http://AgileConsultingLLC.com/
r...@GaslightSoftware.com http://GaslightSoftware.com/

[Vladimir Rybas]

> 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)

On Thu, Dec 9, 2010 at 9:18 AM, Marnen Laibow-Koser
<li...@ruby-forum.com> wrote:
> 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?
>
>
>>

>> Thanks,
>> Buvana
>
> Best,
> --
> Marnen Laibow-Koser
> http://www.marnen.org
> mar...@marnen.org
>
> Sent from my iPhone
>
> --
> Posted via http://www.ruby-forum.com/.
>

[Robert Pankowecki (rupert)]

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
http://robert.pankowecki.pl