Question

Suppose that i have 2 objects, where each one has a particular slot numbered from 1-5 (unique). Say that object1 has slot = 3 and object2 slot = 5.
What is an effective way to create a hash like :

{ 1 => nil, 2 => nil, 3 => object1, 4 => nil, 5 => object2}

I suppose map could be used, but what’s the best way ?

EDIT : 5 is just an example, please pretend that you do not know the number of slots.

Answer 1

require 'ostruct'
objects =[OpenStruct.new(:slot => 3), OpenStruct.new(:slot => 5)]
base = Hash[(1..5).map { |x| [x, nil] }] # also: Hash[(1..5).zip]
#=> {1=>nil, 2=>nil, 3=>nil, 4=>nil, 5=>nil}
merged = base.merge(Hash[objects.map(&:slot).zip(objects)])
#=> {1=>nil, 2=>nil, 3=>#<OpenStruct slot=3>, 4=>nil, 5=>#<OpenStruct slot=5>}

Also:

slots = Hash[objects.map(&:slot).zip(objects)]
#=> {3=>#<OpenStruct slot=3>, 5=>#<OpenStruct slot=5>}
merged = Hash[(1..5).map { |slot| [slot, slots[slot]] }]
#=> {1=>nil, 2=>nil, 3=>#<OpenStruct slot=3>, 4=>nil, 5=>#<OpenStruct slot=5>}