Select into a hash from a Struct in Ruby

Question

I have the following Struct

Struct.new("TestClient", :loc, :type, :ssh, :hostname, :ip)
@clients = [
Struct::TestClient.new(1, "mac", true, "test1", "192.168.1.101"),
Struct::TestClient.new(1, "mac", true, "test2", "192.168.1.102"),
Struct::TestClient.new(1, "mac", true, "test3", "192.168.1.103"),
Struct::TestClient.new(1, "mac", true, "test4", "192.168.1.104"),
]

...and I can select the IP addresses into an array based on the type in the following way.

@clients.select{|c| c.type == "mac"}.map(&:ip)
=> ["192.168.1.101", "192.168.1.102", "192.168.1.103", "192.168.1.104"]

Can anyone enlighten me what would that obvious way be to select 2 variables from the Struct into a hash. e.g. I want to select all the ip and hostnames into a hash based on the "mac" type.

I'm expecting the result to look something like this:

["192.168.1.101"=>"test1", "192.168.1.102"=>"test2", "192.168.1.103"=>"test3", "192.168.1.104"=>"test4"]

Thank You!

Arup Rakshit · Accepted Answer · 2014-03-05 22:15:45Z

2

You can do as below :

Hash[ @clients.map { |c| [c.ip,c.hostname] if c.type == "mac" }.compact ]

Your structure is not a valid Ruby object, rather you would get from the above code the output as below :

{  
   "192.168.1.101"=>"test1", "192.168.1.102"=>"test2", 
   "192.168.1.103"=>"test3", "192.168.1.104"=>"test4" 
}

Edit

# below will also work
@clients.each_with_object({}) do |c,hash| 
    hash[c.ip] = c.hostname if c.type == "mac"
end

edited Mar 5, 2014 at 22:15

answered Mar 5, 2014 at 21:31

Arup Rakshit

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