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Ruby: passing blocks as parameters from oustide class

2017-06-17 19:33 OJAS JUNEJA imported from Stackoverflow

I am getting below error when executing code:

example.rb:9:in `<main>': undefined method `each' for main:Object (NoMethodError)

Line 9 is second last line in my code.

My code:

class TargetProvider
  def each(target,&block)
    block.call(target)
  end   
end

tp = TargetProvider.new
each { puts "Hello!" }
tp.each(1, each)

My motive is to call block with target parameter.

How can I pass a block outside class. Any help please.

2 answers

  • answered 2017-06-17 19:33 Egor Biriukov

    Well, the problem is here:

    tp = TargetProvider.new
each { puts "Hello!" } # Here
tp.each(1, each)

    Here, you are calling each method, not declaring a new variable. In Ruby, if you call a method without specifying its object (via object.method), interpreter searches for that method in MainObject.

    It's clear that there no such method in it, so that's what an error is about.

    What you may want to achieve is looks like this:

    tp = TargetProvider.new
tp.each(1) { puts "Hello!" }

    That code calls TargetProvider's each method passing it a block.

  • answered 2017-06-17 19:33 Fede

    Here is yout code:

    class TargetProvider
  def each(target,&block)
    block.call(target)
  end   
end

tp = TargetProvider.new
each { puts "Hello!" } # this line is trying to run a method called each
tp.each(1, each)

    You need to define a lambda or a proc and store it in a variable, or use the implicit block of the each. Here is an example using a lambda:

    class TargetProvider
  def each(target,&block)
    block.call(target)
  end   
end

tp = TargetProvider.new
each_block = lambda { |a| puts "Hello!" }
tp.each(1, &each_block)

    Here is an example using the implicit block:

    class TargetProvider
  def each(target,&block)
    block.call(target)
  end   
end

tp = TargetProvider.new
each_block = lambda { |a| puts "Hello!" }
tp.each(1) { puts "Hello!" }

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Cookbook Trace:
---------------
/var/chef/cache/cookbooks/docker/libraries/docker_container.rb:319:in `block (3 levels) in <class:DockerContainer>'
/var/chef/cache/cookbooks/docker/libraries/helpers_base.rb:66:in `with_retries'
/var/chef/cache/cookbooks/docker/libraries/docker_container.rb:250:in `block (2 levels) in <class:DockerContainer>'
/var/chef/cache/cookbooks/compat_resource/files/lib/chef_compat/copied_from_chef/chef/provider.rb:81:in `converge_if_changed'
/var/chef/cache/cookbooks/docker/libraries/docker_container.rb:247:in `block in <class:DockerContainer>'
/var/chef/cache/cookbooks/compat_resource/files/lib/chef_compat/copied_from_chef/chef/provider.rb:132:in `instance_eval'
/var/chef/cache/cookbooks/compat_resource/files/lib/chef_compat/copied_from_chef/chef/provider.rb:132:in `compile_and_converge_action'
/var/chef/cache/cookbooks/docker/libraries/docker_container.rb:169:in `call_action'
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Resource Declaration:
---------------------
# In /var/chef/cache/cookbooks/webserver/recipes/default.rb

218:         docker_container container_name do
219:           repo docker[:image]
220:           tag docker[:tag]
221:           #Add all docker link
222:           # links node.set[:linking]
223:           links lazy{node.run_state[:linking]}
224:           env docker[:env]
225:           command docker[:command]
226:           kill_after 30
227:     #      autoremove true
228:           action :redeploy
229:           port docker[:ports]
230:           volumes node.default["bindvolume"]
231:           cap_add 'SYS_ADMIN'
232:           devices []
233:           privileged true
234:           timeout 30
235:     #      {["/dev/fuse"]}
236:         end
237:       else
238:         docker_container container_name do
239:           repo docker[:image]
240:           tag docker[:tag]
241:           #Add all docker link
242:           links node.run_state[:linking]
243:           env docker[:env]
244:           command docker[:command]
245:           kill_after 30
246:     #      autoremove true
247:           action :redeploy
248:           port docker[:ports]
249:           volumes node.default["bindvolume"]
250:           cap_add 'SYS_ADMIN'
251:           devices []
252:           privileged true
253:           timeout 30
254:     #      {["/dev/fuse"]}
255:         end
256:       end
257: 
258:       if (not (defined?(docker[:exec])).nil?) && (not "#{docker[:exec]}" == "")
259:         execute 'execute command inside docker' do
260:         command "docker exec -i #{container_name} /bin/bash -c \'#{docker[:exec]}\'"
261:         end
262:       end
263: 
264:       etchosts.push("#{container_name}:#{container_name}")
265:     end
266: 
267:     #Add proxy.conf to folder if bootproxy defined
268:     if defined?(node[:externalmode]) && node[:externalmode].eql?("bootproxy")
269:       #Prepare bootproxy directories
270:       directory "#{node[:deploycode][:basedirectory]}../bootproxy" do

Compiled Resource:
------------------
# Declared in /var/chef/cache/cookbooks/webserver/recipes/default.rb:218:in `block in from_file'

docker_container("bootproxy") do
  action [:redeploy]
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  cookbook_name "webserver"
  recipe_name "default"
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  repo "daocloud.io/library/nginx"
  tag "stable-alpine"
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  port_bindings {"80/tcp"=>[{"HostIp"=>"0.0.0.0", "HostPort"=>"80"}], "5000/tcp"=>[{"HostIp"=>"0.0.0.0", "HostPort"=>"5000"}]}
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  links #<ChefCompat::CopiedFromChef::Chef::DelayedEvaluator:0x000000055c4a90@/var/chef/cache/cookbooks/webserver/recipes/default.rb:223>
  cap_add ["SYS_ADMIN"]
  privileged true
  timeout 30
  connection #<Docker::Connection:0x00000008301238 @url="unix:///", @options={:socket=>"/var/run/docker.sock", :read_timeout=>60}>
  network_mode "bridge"
  detach true
  signal "SIGTERM"
end

    Running handlers: [2017-03-19T21:20:15+08:00] ERROR: Running exception handlers Running handlers complete [2017-03-19T21:20:15+08:00] ERROR: Exception handlers complete Chef Client failed. 20 resources updated in 34 seconds [2017-03-19T21:20:15+08:00] FATAL: Stacktrace dumped to /var/chef/cache/chef-stacktrace.out [2017-03-19T21:20:15+08:00] ERROR: docker_container[bootproxy] (webserver::default line 218) had an error: Docker::Error::ServerError: Could not get container for bootproxy

    [2017-03-19T21:20:15+08:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

    and here are my codes:

      node.run_state[:linking] = []
  #Special handling if bootproxy,  get all local running docker id and name and link into bootproxy
  if localfolder.eql?("bootproxy")
    container_name = localfolder
    node.set[:dockerinfo] = []
    results = "/tmp/dockerinfo.txt"
    file results do
      action :delete
    end

    cmd = "docker ps -a|grep -v CONTAINER|grep -v monitor|awk \'{print $1, $NF}\'"
    bash cmd do
      code <<-EOH
      #{cmd} > #{results}
      EOH
    end

    ruby_block "result" do
      only_if { "cat #{results}| wc -l;while [ $? -ne 0 ]; do cat #{results}| wc -l;done" }
      # only_if { ::File.exists?(results) }
      block do
        f = File.open(results)
        dockerinfo = Hash.new
        f.each do |line|
          dockerinfo[line.chomp.split(' ')[0]] = line.chomp.split(' ')[1]
        end
        f.close
        node.set[:dockerinfo] = dockerinfo
        node.run_state[:linking] = dockerinfo
        node.run_state[:linking] = []
        node.set[:dockerinfo].each do |hash, dockername|
          node.run_state[:linking].push("#{dockername}:#{dockername}")
        end
      end
    end
  else
    node.run_state[:linking] = etchosts
  end

  if node.default["bindvolume"].eql?([":"])
    node.default["bindvolume"] = nil
  end
  if localfolder.eql?("bootproxy")
    # Using lazy evaluation if bootproxy
    docker_container container_name do
      repo docker[:image]
      tag docker[:tag]
      #Add all docker link
      # links node.set[:linking]
      links lazy{node.run_state[:linking]}
      env docker[:env]
      command docker[:command]
      kill_after 30
#      autoremove true
      action :redeploy
      port docker[:ports]
      volumes node.default["bindvolume"]
      cap_add 'SYS_ADMIN'
      devices []
      privileged true
      timeout 30
#      {["/dev/fuse"]}
    end
  else
    docker_container container_name do
      repo docker[:image]
      tag docker[:tag]
      #Add all docker link
      links node.run_state[:linking]
      env docker[:env]
      command docker[:command]
      kill_after 30
#      autoremove true
      action :redeploy
      port docker[:ports]
      volumes node.default["bindvolume"]
      cap_add 'SYS_ADMIN'
      devices []
      privileged true
      timeout 30
#      {["/dev/fuse"]}
    end
  end

    What i am trying to do here, is to run a set of docker by chef docker cookbook version 2.14.3, with names looping into "localfolder", and when localfolder = "bootproxy", execute bash command to check what dockers are currently running and link them by a nginx docker named as "bootproxy".

    My issue here is, whenever i cleared all my cache or after i have re-uploaded all my cookbook "webserver", chef-client runs fine without error. But when i rerun the chef-client, i got

    Docker::Error::ServerError
--------------------------
Could not get container for bootproxy

    due to the value of "links" in "docker_container" resources became "#" instead of an array that included the current running docker names like [ "container1:container1", "container2:container2", "container3:container3"]. So i suspect that the ruby_block that trying to get value from the host is being cached and not running after the first successive execution. My removal of cache (rm -rf /var/chef/cache) proved it but i cannot define removal of cache inside cookbook(not a neat way to work it out too). I need to make the chef-client able to rerun as i am using it to deploy my set of codes in the whole envionment. Please give me any advise for this.

    Thanks!