1 files changed, 61 insertions, 0 deletions
diff --git a/lib/puppet/util/resource_template.rb b/lib/puppet/util/resource_template.rb
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+++ b/lib/puppet/util/resource_template.rb
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+require 'puppet/util'
+require 'puppet/util/logging'
+require 'erb'
+
+# A template wrapper that evaluates a template in the
+# context of a resource, allowing the resource attributes
+# to be looked up from within the template.
+#  This provides functionality essentially equivalent to
+# the language's template() function.  You pass your file
+# path and the resource you want to use into the initialization
+# method, then call result() on the instance, and you get back
+# a chunk of text.
+#  The resource's parameters are available as instance variables
+# (as opposed to the language, where we use a method_missing trick).
+#  For example, say you have a resource that generates a file.  You would
+# need to implement the following style of `generate` method:
+#
+#   def generate
+#       template = Puppet::Util::ResourceTemplate.new("/path/to/template", self)
+#
+#       return Puppet::Type.type(:file).create :path => "/my/file",
+#           :content => template.evaluate
+#   end
+#
+# This generated file gets added to the catalog (which is what `generate` does),
+# and its content is the result of the template.  You need to use instance
+# variables in your template, so if your template just needs to have the name
+# of the generating resource, it would just have:
+#
+#   <%= @name %>
+#
+# Since the ResourceTemplate class sets as instance variables all of the resource's
+# parameters.
+#
+# Note that this example uses the generating resource as its source of
+# parameters, which is generally most useful, since it allows you to configure
+# the generated resource via the generating resource.
+class Puppet::Util::ResourceTemplate
+    include Puppet::Util::Logging
+
+    def evaluate
+        set_resource_variables
+        ERB.new(File.read(@file), 0, "-").result(binding)
+    end
+
+    def initialize(file, resource)
+        raise ArgumentError, "Template %s does not exist" % file unless FileTest.exist?(file)
+        @file = file
+        @resource = resource
+    end
+
+    private
+
+    def set_resource_variables
+        @resource.to_hash.each do |param, value|
+            var = "@#{param.to_s}"
+            instance_variable_set(var, value)
+        end
+    end
+end
+