diff options
Diffstat (limited to 'guides/source/debugging_rails_applications.md')
| -rw-r--r-- | guides/source/debugging_rails_applications.md | 168 |
1 files changed, 84 insertions, 84 deletions
diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md index b067d9efb7..c1f26c2a5e 100644 --- a/guides/source/debugging_rails_applications.md +++ b/guides/source/debugging_rails_applications.md @@ -26,17 +26,17 @@ One common task is to inspect the contents of a variable. In Rails, you can do t The `debug` helper will return a \<pre> tag that renders the object using the YAML format. This will generate human-readable data from any object. For example, if you have this code in a view: ```html+erb -<%= debug @post %> +<%= debug @article %> <p> <b>Title:</b> - <%= @post.title %> + <%= @article.title %> </p> ``` You'll see something like this: ```yaml ---- !ruby/object:Post +--- !ruby/object Article attributes: updated_at: 2008-09-05 22:55:47 body: It's a very helpful guide for debugging your Rails app. @@ -55,10 +55,10 @@ Title: Rails debugging guide Displaying an instance variable, or any other object or method, in YAML format can be achieved this way: ```html+erb -<%= simple_format @post.to_yaml %> +<%= simple_format @article.to_yaml %> <p> <b>Title:</b> - <%= @post.title %> + <%= @article.title %> </p> ``` @@ -67,7 +67,7 @@ The `to_yaml` method converts the method to YAML format leaving it more readable As a result of this, you will have something like this in your view: ```yaml ---- !ruby/object:Post +--- !ruby/object Article attributes: updated_at: 2008-09-05 22:55:47 body: It's a very helpful guide for debugging your Rails app. @@ -88,7 +88,7 @@ Another useful method for displaying object values is `inspect`, especially when <%= [1, 2, 3, 4, 5].inspect %> <p> <b>Title:</b> - <%= @post.title %> + <%= @article.title %> </p> ``` @@ -153,18 +153,18 @@ logger.fatal "Terminating application, raised unrecoverable error!!!" Here's an example of a method instrumented with extra logging: ```ruby -class PostsController < ApplicationController +class ArticlesController < ApplicationController # ... def create - @post = Post.new(params[:post]) - logger.debug "New post: #{@post.attributes.inspect}" - logger.debug "Post should be valid: #{@post.valid?}" - - if @post.save - flash[:notice] = 'Post was successfully created.' - logger.debug "The post was saved and now the user is going to be redirected..." - redirect_to(@post) + @article = Article.new(params[:article]) + logger.debug "New article: #{@article.attributes.inspect}" + logger.debug "Article should be valid: #{@article.valid?}" + + if @article.save + flash[:notice] = 'Article was successfully created.' + logger.debug "The article was saved and now the user is going to be redirected..." + redirect_to(@article) else render action: "new" end @@ -177,21 +177,21 @@ end Here's an example of the log generated when this controller action is executed: ``` -Processing PostsController#create (for 127.0.0.1 at 2008-09-08 11:52:54) [POST] +Processing ArticlesController#create (for 127.0.0.1 at 2008-09-08 11:52:54) [POST] Session ID: BAh7BzoMY3NyZl9pZCIlMDY5MWU1M2I1ZDRjODBlMzkyMWI1OTg2NWQyNzViZjYiCmZsYXNoSUM6J0FjdGl vbkNvbnRyb2xsZXI6OkZsYXNoOjpGbGFzaEhhc2h7AAY6CkB1c2VkewA=--b18cd92fba90eacf8137e5f6b3b06c4d724596a4 - Parameters: {"commit"=>"Create", "post"=>{"title"=>"Debugging Rails", + Parameters: {"commit"=>"Create", "article"=>{"title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!", "published"=>"0"}, - "authenticity_token"=>"2059c1286e93402e389127b1153204e0d1e275dd", "action"=>"create", "controller"=>"posts"} -New post: {"updated_at"=>nil, "title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!", + "authenticity_token"=>"2059c1286e93402e389127b1153204e0d1e275dd", "action"=>"create", "controller"=>"articles"} +New article: {"updated_at"=>nil, "title"=>"Debugging Rails", "body"=>"I'm learning how to print in logs!!!", "published"=>false, "created_at"=>nil} -Post should be valid: true - Post Create (0.000443) INSERT INTO "posts" ("updated_at", "title", "body", "published", +Article should be valid: true + Article Create (0.000443) INSERT INTO "articles" ("updated_at", "title", "body", "published", "created_at") VALUES('2008-09-08 14:52:54', 'Debugging Rails', 'I''m learning how to print in logs!!!', 'f', '2008-09-08 14:52:54') -The post was saved and now the user is going to be redirected... -Redirected to #<Post:0x20af760> -Completed in 0.01224 (81 reqs/sec) | DB: 0.00044 (3%) | 302 Found [http://localhost/posts] +The article was saved and now the user is going to be redirected... +Redirected to # Article:0x20af760> +Completed in 0.01224 (81 reqs/sec) | DB: 0.00044 (3%) | 302 Found [http://localhost/articles] ``` Adding extra logging like this makes it easy to search for unexpected or unusual behavior in your logs. If you add extra logging, be sure to make sensible use of log levels to avoid filling your production logs with useless trivia. @@ -286,17 +286,17 @@ Before the prompt, the code around the line that is about to be run will be displayed and the current line will be marked by '=>'. Like this: ``` -[1, 10] in /PathTo/project/app/controllers/posts_controller.rb +[1, 10] in /PathTo/project/app/controllers/articles_controller.rb 3: - 4: # GET /posts - 5: # GET /posts.json + 4: # GET /articles + 5: # GET /articles.json 6: def index 7: byebug -=> 8: @posts = Post.find_recent +=> 8: @articles = Article.find_recent 9: 10: respond_to do |format| 11: format.html # index.html.erb - 12: format.json { render json: @posts } + 12: format.json { render json: @articles } (byebug) ``` @@ -309,7 +309,7 @@ For example: ```bash => Booting WEBrick -=> Rails 4.1.0 application starting in development on http://0.0.0.0:3000 +=> Rails 4.1.1 application starting in development on http://0.0.0.0:3000 => Run `rails server -h` for more startup options => Notice: server is listening on all interfaces (0.0.0.0). Consider using 127.0.0.1 (--binding option) => Ctrl-C to shutdown server @@ -320,19 +320,19 @@ For example: Started GET "/" for 127.0.0.1 at 2014-04-11 13:11:48 +0200 ActiveRecord::SchemaMigration Load (0.2ms) SELECT "schema_migrations".* FROM "schema_migrations" -Processing by PostsController#index as HTML +Processing by ArticlesController#index as HTML -[3, 12] in /PathTo/project/app/controllers/posts_controller.rb +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb 3: - 4: # GET /posts - 5: # GET /posts.json + 4: # GET /articles + 5: # GET /articles.json 6: def index 7: byebug -=> 8: @posts = Post.find_recent +=> 8: @articles = Article.find_recent 9: 10: respond_to do |format| 11: format.html # index.html.erb - 12: format.json { render json: @posts } + 12: format.json { render json: @articles } (byebug) ``` @@ -365,15 +365,15 @@ To see the previous ten lines you should type `list-` (or `l-`) ``` (byebug) l- -[1, 10] in /PathTo/project/app/controllers/posts_controller.rb - 1 class PostsController < ApplicationController - 2 before_action :set_post, only: [:show, :edit, :update, :destroy] +[1, 10] in /PathTo/project/app/controllers/articles_controller.rb + 1 class ArticlesController < ApplicationController + 2 before_action :set_article, only: [:show, :edit, :update, :destroy] 3 - 4 # GET /posts - 5 # GET /posts.json + 4 # GET /articles + 5 # GET /articles.json 6 def index 7 byebug - 8 @posts = Post.find_recent + 8 @articles = Article.find_recent 9 10 respond_to do |format| @@ -386,17 +386,17 @@ the code again you can type `list=` ``` (byebug) list= -[3, 12] in /PathTo/project/app/controllers/posts_controller.rb +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb 3: - 4: # GET /posts - 5: # GET /posts.json + 4: # GET /articles + 5: # GET /articles.json 6: def index 7: byebug -=> 8: @posts = Post.find_recent +=> 8: @articles = Article.find_recent 9: 10: respond_to do |format| 11: format.html # index.html.erb - 12: format.json { render json: @posts } + 12: format.json { render json: @articles } (byebug) ``` @@ -419,14 +419,14 @@ then `backtrace` will supply the answer. ``` (byebug) where ---> #0 PostsController.index - at /PathTo/project/test_app/app/controllers/posts_controller.rb:8 +--> #0 ArticlesController.index + at /PathTo/project/test_app/app/controllers/articles_controller.rb:8 #1 ActionController::ImplicitRender.send_action(method#String, *args#Array) - at /PathToGems/actionpack-4.1.0/lib/action_controller/metal/implicit_render.rb:4 + at /PathToGems/actionpack-4.1.1/lib/action_controller/metal/implicit_render.rb:4 #2 AbstractController::Base.process_action(action#NilClass, *args#Array) - at /PathToGems/actionpack-4.1.0/lib/abstract_controller/base.rb:189 + at /PathToGems/actionpack-4.1.1/lib/abstract_controller/base.rb:189 #3 ActionController::Rendering.process_action(action#NilClass, *args#NilClass) - at /PathToGems/actionpack-4.1.0/lib/action_controller/metal/rendering.rb:10 + at /PathToGems/actionpack-4.1.1/lib/action_controller/metal/rendering.rb:10 ... ``` @@ -438,7 +438,7 @@ context. ``` (byebug) frame 2 -[184, 193] in /PathToGems/actionpack-4.1.0/lib/abstract_controller/base.rb +[184, 193] in /PathToGems/actionpack-4.1.1/lib/abstract_controller/base.rb 184: # is the intended way to override action dispatching. 185: # 186: # Notice that the first argument is the method to be dispatched @@ -487,17 +487,17 @@ This example shows how you can print the instance variables defined within the current context: ``` -[3, 12] in /PathTo/project/app/controllers/posts_controller.rb +[3, 12] in /PathTo/project/app/controllers/articles_controller.rb 3: - 4: # GET /posts - 5: # GET /posts.json + 4: # GET /articles + 5: # GET /articles.json 6: def index 7: byebug -=> 8: @posts = Post.find_recent +=> 8: @articles = Article.find_recent 9: 10: respond_to do |format| 11: format.html # index.html.erb - 12: format.json { render json: @posts } + 12: format.json { render json: @articles } (byebug) instance_variables [:@_action_has_layout, :@_routes, :@_headers, :@_status, :@_request, @@ -512,15 +512,15 @@ command later in this guide). ``` (byebug) next -[5, 14] in /PathTo/project/app/controllers/posts_controller.rb - 5 # GET /posts.json +[5, 14] in /PathTo/project/app/controllers/articles_controller.rb + 5 # GET /articles.json 6 def index 7 byebug - 8 @posts = Post.find_recent + 8 @articles = Article.find_recent 9 => 10 respond_to do |format| 11 format.html # index.html.erb - 12 format.json { render json: @posts } + 12 format.json { render json: @articles } 13 end 14 end 15 @@ -530,11 +530,11 @@ command later in this guide). And then ask again for the instance_variables: ``` -(byebug) instance_variables.include? "@posts" +(byebug) instance_variables.include? "@articles" true ``` -Now `@posts` is included in the instance variables, because the line defining it +Now `@articles` is included in the instance variables, because the line defining it was executed. TIP: You can also step into **irb** mode with the command `irb` (of course!). @@ -564,7 +564,7 @@ example, to check that we have no local variables currently defined. You can also inspect for an object method this way: ``` -(byebug) var instance Post.new +(byebug) var instance Article.new @_start_transaction_state = {} @aggregation_cache = {} @association_cache = {} @@ -581,8 +581,8 @@ You can use also `display` to start watching variables. This is a good way of tracking the values of a variable while the execution goes on. ``` -(byebug) display @posts -1: @posts = nil +(byebug) display @articles +1: @articles = nil ``` The variables inside the displaying list will be printed with their values after @@ -611,10 +611,10 @@ For example, consider the following situation: ```ruby Started GET "/" for 127.0.0.1 at 2014-04-11 13:39:23 +0200 -Processing by PostsController#index as HTML +Processing by ArticlesController#index as HTML -[1, 8] in /home/davidr/Proyectos/test_app/app/models/post.rb - 1: class Post < ActiveRecord::Base +[1, 8] in /home/davidr/Proyectos/test_app/app/models/article.rb + 1: class Article < ActiveRecord::Base 2: 3: def self.find_recent(limit = 10) 4: byebug @@ -634,15 +634,15 @@ the method, so `byebug` will jump to next next line of the previous frame. (byebug) next Next went up a frame because previous frame finished -[4, 13] in /PathTo/project/test_app/app/controllers/posts_controller.rb - 4: # GET /posts - 5: # GET /posts.json +[4, 13] in /PathTo/project/test_app/app/controllers/articles_controller.rb + 4: # GET /articles + 5: # GET /articles.json 6: def index - 7: @posts = Post.find_recent + 7: @articles = Article.find_recent 8: => 9: respond_to do |format| 10: format.html # index.html.erb - 11: format.json { render json: @posts } + 11: format.json { render json: @articles } 12: end 13: end @@ -655,7 +655,7 @@ instruction to be executed. In this case, the activesupport's `week` method. ``` (byebug) step -[50, 59] in /PathToGems/activesupport-4.1.0/lib/active_support/core_ext/numeric/time.rb +[50, 59] in /PathToGems/activesupport-4.1.1/lib/active_support/core_ext/numeric/time.rb 50: ActiveSupport::Duration.new(self * 24.hours, [[:days, self]]) 51: end 52: alias :day :days @@ -693,20 +693,20 @@ _expression_ works the same way as with file:line. For example, in the previous situation ``` -[4, 13] in /PathTo/project/app/controllers/posts_controller.rb - 4: # GET /posts - 5: # GET /posts.json +[4, 13] in /PathTo/project/app/controllers/articles_controller.rb + 4: # GET /articles + 5: # GET /articles.json 6: def index - 7: @posts = Post.find_recent + 7: @articles = Article.find_recent 8: => 9: respond_to do |format| 10: format.html # index.html.erb - 11: format.json { render json: @posts } + 11: format.json { render json: @articles } 12: end 13: end (byebug) break 11 -Created breakpoint 1 at /PathTo/project/app/controllers/posts_controller.rb:11 +Created breakpoint 1 at /PathTo/project/app/controllers/articles_controller.rb:11 ``` @@ -716,7 +716,7 @@ supply a number, it lists that breakpoint. Otherwise it lists all breakpoints. ``` (byebug) info breakpoints Num Enb What -1 y at /PathTo/project/app/controllers/posts_controller.rb:11 +1 y at /PathTo/project/app/controllers/articles_controller.rb:11 ``` To delete breakpoints: use the command `delete _n_` to remove the breakpoint |