Chef derived attribute

app-attributes-default.rb

  default["app"]["name"] = "app"
  
  # Attribute to show the problem
  default["app"]["install_dir"] = "/home/#{node["app"]["name"]}"
  
  # Attribute used in delayed evaluation approach
  default["app"]["install_dir2"] = "/home/%{name}"

  # Attribute used in conditional assignment approach
  # default["app"]["install_dir3"] = "/home/#{node["app"]["name"]}"

app-recipes-conditional.rb

#
# Cookbook Name::app
# Recipe:: conditional
#

install_dir = node['app']['install_dir3'] || "/var/#{node['app']['name']}"

# Alternative to line above that will set the node attribute
#node.default['app']['install_dir3'] = "/var/#{node['app']['name']}" unless node['app']['install_dir3']
#install_dir = node['app']['install_dir3']

ruby_block "Executing resource in recipe" do
  block do
    Log.info "Executing recipe, application name is: #{node['app']['name'] };" +
      " install_dir is #{install_dir}"  
  end
end

app-recipes-default.rb

#
# Cookbook Name:: app
# Recipe:: default
#

ruby_block "Executing resource in recipe" do
  block do
    Log.info "Executing recipe, application name is: #{node['app']['name'] };" +
      " install_dir is #{node['app']['install_dir']}"  
  end
end

app-recipes-delayed.rb

#
# Cookbook Name:: app
# Recipe:: delayed
#

install_dir = node['app']['install_dir2'] % { name: node['app']['name'] }

ruby_block "Executing resource in recipe" do
  block do
    Log.info "Executing recipe, application name is: #{node['app']['name'] };" +
      " install_dir is #{install_dir}"  
  end
end

my_app-attributes-default.rb

  default["app"]["name"] = "my_app"

# Uncomment these to test that the install_dir can be overridden
#  default["app"]["install_dir"] = "/tmp"
#  default["app"]["install_dir2"] = "/tmp"
#  default["app"]["install_dir3"] = "/tmp"