廚師食譜中的Ruby語法

Question

伙計我對紅寶石沒有任何線索，但卻不得不玩廚師食譜 。 有人可以幫助我解決語法問題嗎？

運行配方時，這些行會導致問題

old_configs = node["monitoring"]["configs"] || []

例外是：

NoMethodError: undefined method `[]' for nil:NilClass /var/chef/cache/cookbooks/collectd/recipes/default.rb:100:in `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/mixin/from_file.rb:30:in `instance_eval'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/mixin/from_file.rb:30:in `from_file'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/cookbook_version.rb:237:in `load_recipe'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context.rb:151:in `load_recipe'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:139:in `block in compile_recipe
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:137:in `each'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:137:in `compile_recipes'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context/cookbook_compiler.rb:74:in `compile'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/run_context.rb:86:in `load'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:249:in `setup_run_context'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:492:in `do_run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:199:in `block in run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:193:in `fork' 
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/client.rb:193:in `run' 
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application.rb:183:in `run_chef_client'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:302:in `block in run_application'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:294:in `loop'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application/client.rb:294:in `run_application'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/lib/chef/application.rb:66:in `run'
/opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.6.0/bin/chef-client:26:in `<top (required)>'

Answer 1

這可能是由於節點“監控”屬性不存在這一事實，在嘗試查找節點[“監控”] [“配置”]之前，應首先檢查節點[“監控”]是否存在

這樣做的簡單方法是：

if node["monitoring"]
  old_configs = node["monitoring"]["configs"] || []
end