Created
June 7, 2013 01:58
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# First: Product - Default without setting hash defaults: | |
x = %w(a b c) | |
h = Hash[x.product([true])] | |
p h # => {'a' => true, 'b' => true, 'c' => true} | |
p h['a'] # => true | |
p h['d'] # => nil | |
# e.g: sphinx takes a hash of field name -> weight pairs, so we use | |
def search_weights | |
@search_weights ||= Hash[fields.product([25]) + sanitized_fields.product([1])] | |
end | |
# to generate the hash. | |
# Second: normal default | |
i = Hash.new(false) | |
p i # => {} | |
p i['a'] # => false | |
p i # => {} | |
# With a block | |
j = Hash.new { |h,k| h[k] = false } | |
p i # => {} | |
p i['a'] # => false | |
p i # => {'a' => false} | |
# Now, doing magic! - Super useful for data munging. | |
k = Hash.new { |h,k| h[k] = [] } | |
%w(a b c d).each_with_index do |key, idx| | |
k[key] << idx | |
end | |
p k # => {"a"=>[0], "b"=>[1], "c"=>[2], "d"=>[3]} | |
# And, for the grand finale: | |
k = Hash.new { |h,k| h[k] = Hash.new(&h.default_proc) } | |
p k # => {} | |
p k[:a][:b][:c] # => {} | |
p k # => {:a=>{:b=>{:c=>{}}}} |
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