Ruby hash of hash of hash
-
25-05-2021 - |
Question
How can I have a hash of hash of hash?
My test returns
undefined method `[]' for nil:NilClass (NoMethodError)
Any tips?
found = Hash.new()
x = 1;
while x < 4 do
found[x] = Hash.new()
y = 1
while y < 4 do
found[x][y] = Hash.new()
found[x][y]['name1'] = 'abc1'
found[x][y]['name2'] = 'abc2'
found[x][y]['name3'] = 'abc3'
y += 1
end
x += 1
end
found.each do |k, v, y|
puts "k : #{k}"
puts " : #{v[y['name1']]}"
puts " : #{v[y['name2']]}"
puts " : #{v[y['name3']]}"
puts
end
Solution
I think you want something like this:
First of all create the data structure. You want nested hashes so you need to define default values for each hash key.
found = Hash.new do |hash,key|
hash[key] = Hash.new do |hash,key|
hash[key] = Hash.new
end
end
Run the search
(1..3).each do |x|
(1..3).each do |y|
found[x][y]['name1'] = 'abc1'
found[x][y]['name2'] = 'abc1'
found[x][y]['name3'] = 'abc1'
end
end
Then display the results
found.each do |x, y_hash|
y_hash.each do |y, name_hash|
name_hash.each do |name, value|
puts "#{x} => #{y} => #{name} => #{value}"
end
end
end
OTHER TIPS
The way you build the hash seems to be functional. What probably causes the error is this loop:
found.each do |k, v, y|
Hash#each
yields key/value pairs, so y
will be assigned nil
, thus causing the error two lines below. What you probably meant is a nested loop like
found.each do |x, h1|
h1.each do |y, h2|
puts h2['name1']
end
end
You should also be aware that you can write these kinds of counting loops more concisely in Ruby:
found = Hash.new { |h,k| h[k] = {} }
1.upto(3) do |x|
1.upto(3) do |y|
found[x][y] = {
'name1' => 'abc1',
'name2' => 'abc2',
'name3' => 'abc3',
}
end
end
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