Flatten out Hash

[Glenn Ritz]

Hi,

I would like to take a nested hash that looks like this:

{"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}

and turn it into an array of 2 element arrays like this:

[["a: b2: c2: ", 2], ["a: b: c: ", 1]]

Is there a simple way to do this? I wrote a method that iterates
through the nested hashes recursively, but it's a bit cumbersome.

 

[Jean G.]

Hi,

I would like to take a nested hash that looks like this:

{"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}

and turn it into an array of 2 element arrays like this:

[["a: b2: c2: ", 2], ["a: b: c: ", 1]]

My method:

hash = {"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}
array = []

hash.keys.each do |k1|
hash[k1].keys.each do |k2|
hash[k1][k2].keys.each do |k3|
array << ["#{k1}: #{k2}: #{k3}:",hash[k1][k2][k3]]
end
end
end

 

[Glenn Ritz]

Hi,

I would like to take a nested hash that looks like this:

{"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}

and turn it into an array of 2 element arrays like this:

[["a: b2: c2: ", 2], ["a: b: c: ", 1]]

My method:

hash = {"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}
array = []

hash.keys.each do |k1|
hash[k1].keys.each do |k2|
hash[k1][k2].keys.each do |k3|
array << ["#{k1}: #{k2}: #{k3}:",hash[k1][k2][k3]]
end
end
end

Thanks, Jean.

It's a good solution. But it's dependent on there being 3 levels of
hashes. What if you didn't know how many levels of nesting there was
before executing the code? Suppose the hash looked like this instead:

{"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=> {"d2" => 2}}}}

 

[Brian Candler]

Hi,

I would like to take a nested hash that looks like this:

{"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}

and turn it into an array of 2 element arrays like this:

[["a: b2: c2: ", 2], ["a: b: c: ", 1]]

Is there a simple way to do this? I wrote a method that iterates
through the nested hashes recursively, but it's a bit cumbersome.

I think that's the right way, if the nesting depth is variable. One
example:

class Hash
def flat_each(prefix="", &blk)
each do |k,v|
if v.is_a?(Hash)
v.flat_each(prefix+k+": ", &blk)
else
yield prefix+k, v
end
end
end
end

require 'enumerator'
h = {"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}
p h.to_enumflat_each).collect { |k,v| [k,v] }

 

[Brian Candler]

Perhaps a better solution is to yield an array of keys (being the 'path'
to reach the end node), because then the caller can choose how to
combine them.

class Hash
def flat_each(prefix=[], &blk)
each do |k,v|
if v.is_a?(Hash)
v.flat_each(prefix+[k], &blk)
else
yield prefix+[k], v
end
end
end
end

require 'enumerator'
h = {"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=>2}}}
h = {"a"=>{"b"=>{"c"=>1}, "b2"=>{"c2"=> {"d2" => 2}}}}
p h.to_enumflat_each).collect { |k,v| [k.join(": "),v] }
h.flat_each do |k,v|
puts "#{k.join("/")} => #{v}"
end

 

[Robert Klemme]

Hi,

I would like to take a nested hash that looks like this:

{"a"=3D>{"b"=3D>{"c"=3D>1}, "b2"=3D>{"c2"=3D>2}}}

and turn it into an array of 2 element arrays like this:

[["a: b2: c2: ", 2], ["a: b: c: ", 1]]

My method:

hash =3D {"a"=3D>{"b"=3D>{"c"=3D>1}, "b2"=3D>{"c2"=3D>2}}}
array =3D []

hash.keys.each do |k1|
=A0 =A0 hash[k1].keys.each do |k2|
=A0 =A0 =A0 =A0 hash[k1][k2].keys.each do |k3|
=A0 =A0 =A0 =A0 =A0 =A0 =A0array << ["#{k1}: #{k2}: #{k3}:",hash[k1][k2]= [k3]]
=A0 =A0 =A0 =A0 end
=A0 =A0 end
end

Thanks, Jean.

It's a good solution. =A0But it's dependent on there being 3 levels of
hashes. =A0What if you didn't know how many levels of nesting there was
before executing the code? =A0Suppose the hash looked like this instead:

{"a"=3D>{"b"=3D>{"c"=3D>1}, "b2"=3D>{"c2"=3D> {"d2" =3D> 2}}}}

Basically you want to do a DFS and store the path to the root for
every leaf. Something like http://gist.github.com/326558

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/