Nested hash defined?()
defined, hash, hash-of-hashes, ruby
Solution
When using ActiveSupport (Rails) or Backports, you can use `try`:
@hash[:key1].try(:fetch, :key2)
You could even handle `@hash` being `nil`:
@hash.try(:fetch, :key1).try(:fetch, :key2)
If you want `@hash` to always return a hash for a missing key:
@hash = Hash.new { |h,k| h[k] = {} }
@hash[:foo] # => {}
You could also define this recursive:
def recursive_hash
Hash.new { |h,k| h[k] = recursive_hash }
end
@hash = recursive_hash
@hash[:foo][:bar][:blah] = 10
@hash # => {:foo => {:bar => {:blah => 10}}}
But to answer your question:
module HasNestedKey
Hash.send(:include, self)
def has_nested_key?(*args)
return false unless sub = self[args.shift]
return true if args.empty?
sub.respond_to?(:has_nested_key?) and sub.has_nested_key?(*args)
end
end
@hash.has_nested_key? :key1, :key2
Problem
What's the most concise way to determine if `@hash[:key1][:key2]` is defined, that does not throw an error if `@hash` or `@hash[:key1]` are nil? `defined?(@hash[:key1][:key2])` returns True if `@hash[:key1]` exists (it does not determine whether `:key2` is defined)