this is an example usage of iterators in puppet 3.4

puppet_iteration.pp

# challenge: write an ini file from hiera input


# $cache_cluster_instances = [ 
#   { host => 'cache-a', weight => 1 },
#   { host => 'cache-b', weight => 0.5 },
#   { host => 'cache-c', weight => 0.5 },
# ]
$cache_cluster_instances = hiera('cache_cluster_instances')

$cache_cluster_instances.each |$i, $cache_cluster_instance| {

  Ini_Setting {
    ensure => present,
    path    => '/tmp/myapp.ini',
  }

  ini_setting { "cache_instance${i}_host" :
    section => 'cache_cluster',
    setting => "${i}.host",
    value   => $cache_cluster_instance['host'],
  }
  ini_setting { "cache_instance${i}_weight" :
    section => 'cache_cluster',
    setting => "${i}.weight",
    value   => $cache_cluster_instance['weight'],
  }
}

###
# "with create_resources":
###

# $cache_cluster_instances = [ 
#   { host => 'cache-a', weight => 1 },
#   { host => 'cache-b', weight => 0.5 },
#   { host => 'cache-c', weight => 0.5 },
# ]
$cache_cluster_instances = hiera('cache_cluster_instances')
cache_cluster_instances_to_ini('my cache cluster', $cache_cluster_instances)

define cache_cluster_instances_to_ini(
  $instances
) {
  $ini_settings_defaults = {
    ensure => present,
    path    => '/tmp/myapp.ini',
  }

  $ini_settings = { 
    "cache_instance${i}_host" => {
       section => 'cache_cluster',
       setting => "${1}.host",
       value   => $cache_cluster_instance['host'],
    },
    "cache_instance${i}_weight" => {
      section => 'cache_cluster',
      setting => "${1}.weight",
      value   => $cache_cluster_instance['weight'],
    }
  }

  create_resources('ini_setting', $ini_settings, $ini_settings_defaults)
}