harper
1
is there a nice clean method to do the following:
a = Module.new(:att1 => 1, :att2 => “abc”)
b = Module.new(:att1 => 1, :att2 => “adfbc”)
c = Module.new(:att1 => 2, :att2 => “abcasdf”)
d = Module.new(:att1 => 1, :att2 => “ddddf”)
e = Module.new(:att1 => 2, :att2 => “ddddf”)
f = Module.new(:att1 => 3, :att2 => “ddddf”)
array = [a,b,c,d,e,f]
i want to take the ‘array’ var and make it into seperate arrays
according to the att1 attribute, i.e, resulting in the example above to
r1=[a,b,d]
r2=[c,e]
r3=[f]
any nice way to do this?
thx
harper
2
Shai R. wrote:
any nice way to do this?
array.inject({}) { |h,e| (h[e.att1] ||= []) << e; h }
harper
3
Alle domenica 8 luglio 2007, Shai R. ha scritto:
array = [a,b,c,d,e,f]
thx
You can do this (assuming that the objects in array have a method which
returns the value of att1):
array.inject(Hash.new{|hash, key| hash[k] = []}) do |res, i|
res[i.att1] << i
res
end
This will return the following hash:
{
1 => [a, b, d],
2 => [c, e],
3 => [f]
}
If you don’t need to keep the items sorted, a more elegant way would be
to use
a Set instead of an array:
require ‘set’
set = Set.new([a,b,c,d,e,f])
set.classify{|i| i.att1}
This returns an hash analogous to the previous one, but with arrays
replaced
by sets:
{
1 => Set:{a,b,d}
2 => Set:{c,e}
3 => Set:{f}
}
You can then convert those Sets to arrays using their to_a method.
I hope this helps
Stefano
harper
4
El Jul 8, 2007, a las 11:28 AM, Shai R.
escribió:
a = Module.new(:att1 => 1, :att2 => “abc”)
harper
5
Shai R. wrote:
is there a nice clean method to do the following:
i want to take the ‘array’ var and make it into seperate arrays
according to the att1 attribute, i.e, resulting in the example above to
I keep ‘group_by’ (stolen from ActiveSupport) on me for just such
situations:
module Enumerable
def group_by
inject({}) do |groups, element|
(groups[yield(element)] ||= []) << element
groups
end
end
end
array.group_by {|el| el.att1}
best,
Dan
harper
7
El Jul 8, 2007, a las 11:28 AM, Shai R.
escribió:
according to the att1 attribute, i.e, resulting in the example
above to
r1=[a,b,d]
r2=[c,e]
r3=[f]
any nice way to do this?
I would delegate the job to Set#classify.
– fxn
