Accessing Ruby Hash value using a string - ruby-on-rails

Question

I have a ruby array like below
tomcats = [
'sandbox',
'sandbox_acserver',
'sandbox_vgw'
]
I need to pass the string as a hash index like below
tomcats.each do |tomcat_name|
obi_tomcat '#{tomcat_name}' do
Chef::Log::info("Creating tomcat instance - #{tomcat_name}")
Chef::Log::info("#{node['obi']['tomcat']['sandbox'][:name]}") // works
Chef::Log::info("#{node['obi']['tomcat']['#{tomcat_name}'][:name]}") // doesn't work
end
end
The last log throws an error since the access with #{tomcat_name} is nil. I'm new to ruby. How do I access with key as the tomcat_name ?

Answer 1

In normal code, you'd write:
node['obi']['tomcat'][tomcat_name][:name]
In a string interpolation (useless here, because it's the only thing in the string in this case), it is completely the same:
"#{node['obi']['tomcat'][tomcat_name][:name]}"

Answer 2

#{} only works in double quote, as "#{tomcat_name}".
But you don't need the syntax here, just use [tomcat_name] directly.

Answer 3

When I saw this question, I'm thinking whether ruby placeholder could be put inside other placeholder in string interpolation. And I found that ruby actually support it, and most interesting thing is that you don't need to escape the " inside the string.
Although it is not very useful in this case, it still works if you write as below:
Chef::Log::info("#{node['obi']['tomcat']["#{tomcat_name}"][:name]}")
Below is an simple example of placeholder inside other placeholder:
tomcats = [
'sandbox',
'sandbox_acserver',
'sandbox_vgw'
]
node = {
'sandbox_name' => "sandbox name",
'sandbox_acserver_name' => "sandbox_acserver name",
'sandbox_vgw_name' => "sandbox_vgw name",
}
tomcats.each do | tomcat |
puts "This is tomcat : #{node["#{tomcat}_name"]}"
end