Subselecting hash back into hash (oneliner?)

[Jon Baer]

Going through pick-axe and was just wondering if there was a one
liner for something such as this that I may have missed:

h2 = Hash.new
h1 = {"foo1"=>"bar1", "foo2"=>"bar2"}
query = h1.select { |k,v| v == "bar2" }
query.each do |result|
h2[result[0]] = result[1]
end
p h2

Thanks.

- Jon

 

[James Edward Gray II]

Going through pick-axe and was just wondering if there was a one
liner for something such as this that I may have missed:

h2 = Hash.new
h1 = {"foo1"=>"bar1", "foo2"=>"bar2"}
query = h1.select { |k,v| v == "bar2" }
query.each do |result|
h2[result[0]] = result[1]
end
p h2

Like this?

h1 = {"foo1"=>"bar1", "foo2"=>"bar2"} => {"foo1"=>"bar1", "foo2"=>"bar2"}
h2 = Hash[*h1.select { |k, v| v == "bar2" }.flatten]

=> {"foo2"=>"bar2"}

Hope that helps.

James Edward Gray II

 

[Jon Baer]

Nice .. well that works but in the constructor can you tell me
what "*" would literally "mean"?

Does this just take only an Array obj or could you place any object
in there w/ public attributes/methods?

(Was this covered in pick-axe somewhere I missed?)

Thank you, much appreciated ...

- Jon

h1 = {"foo1"=>"bar1", "foo2"=>"bar2"} => {"foo1"=>"bar1", "foo2"=>"bar2"}
h2 = Hash[*h1.select { |k, v| v == "bar2" }.flatten]

 

[Pit Capitain]

I just looked an can't seem to find it. It's the opposite of the *
operator described on page 347 (explodes an Array out, instead of
collecting it in).

Pickaxe 1, page 229, "Invoking a Method". Online here:

http://phrogz.net/ProgrammingRuby/language.html#invokingamethod

Regards,
Pit