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Modularize managing hosts guide (theforeman#925)
Jan 7, 2022
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ref_parsing-arrays.adoc

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Parsing Arrays

While writing or modifying templates, you might encounter variables that return arrays. For example, host variables related to network interfaces, such as @host.interfaces or @host.bond_interfaces, return interface data grouped in an array. To extract a parameter value of a specific interface, use Ruby methods to parse the array.

Finding the Correct Method to Parse an Array

The following procedure is an example that you can use to find the relevant methods to parse arrays in your template. In this example, a report template is used, but the steps are applicable to other templates.

  1. To retrieve the NIC of a content host, in this example, using the @host.interfaces variable returns class values that you can then use to find methods to parse the array.

    Example input:
    <%= @host.interfaces -%>
    Example rendering:
    <Nic::Base::ActiveRecord_Associations_CollectionProxy:0x00007f734036fbe0>

  2. In the Create Template window, click the Help tab and search for the ActiveRecord_Associations_CollectionProxy and Nic::Base classes.

  3. For ActiveRecord_Associations_CollectionProxy, in the Allowed methods or members column, you can view the following methods to parse the array:

    [] each find_in_batches first map size to_a

  4. For Nic::Base, in the Allowed methods or members column, you can view the following method to parse the array:

    alias? attached_devices attached_devices_identifiers attached_to bond_options children_mac_addresses domain fqdn identifier inheriting_mac ip ip6 link mac managed? mode mtu nic_delay physical? primary provision shortname subnet subnet6 tag virtual? vlanid

  5. To iterate through an interface array, add the relevant methods to the ERB syntax:

    Example input:
    <% load_hosts().each_record do |host| -%>
<%    host.interfaces.each do |iface| -%>
  iface.alias?: <%= iface.alias? %>
  iface.attached_to: <%= iface.attached_to %>
  iface.bond_options: <%= iface.bond_options %>
  iface.children_mac_addresses: <%= iface.children_mac_addresses %>
  iface.domain: <%= iface.domain %>
  iface.fqdn: <%= iface.fqdn %>
  iface.identifier: <%= iface.identifier %>
  iface.inheriting_mac: <%= iface.inheriting_mac %>
  iface.ip: <%= iface.ip %>
  iface.ip6: <%= iface.ip6 %>
  iface.link: <%= iface.link %>
  iface.mac: <%= iface.mac %>
  iface.managed?: <%= iface.managed? %>
  iface.mode: <%= iface.mode %>
  iface.mtu: <%= iface.mtu %>
  iface.physical?: <%= iface.physical? %>
  iface.primary: <%= iface.primary %>
  iface.provision: <%= iface.provision %>
  iface.shortname: <%= iface.shortname %>
  iface.subnet: <%= iface.subnet %>
  iface.subnet6: <%= iface.subnet6 %>
  iface.tag: <%= iface.tag %>
  iface.virtual?: <%= iface.virtual? %>
  iface.vlanid: <%= iface.vlanid %>
<%- end -%>
    Example rendering:
    host1.example.com
  iface.alias?: false
  iface.attached_to:
  iface.bond_options:
  iface.children_mac_addresses: []
  iface.domain:
  iface.fqdn: host1.example.com
  iface.identifier: ens192
  iface.inheriting_mac: 00:50:56:8d:4c:cf
  iface.ip: 10.10.181.13
  iface.ip6:
  iface.link: true
  iface.mac: 00:50:56:8d:4c:cf
  iface.managed?: true
  iface.mode: balance-rr
  iface.mtu:
  iface.physical?: true
  iface.primary: true
  iface.provision: true
  iface.shortname: host1.example.com
  iface.subnet:
  iface.subnet6:
  iface.tag:
  iface.virtual?: false
  iface.vlanid: