Low level Helpers

tap_init!

tap_init!(class) - tracks a class’ instance initialization

calls = []
tap_init!(Student) do |payload|
  calls << [payload[:method_name], payload[:arguments]]
end

Student.new("Stan", 18)
Student.new("Jane", 23)

puts(calls.to_s) #=> [[:initialize, {:name=>"Stan", :age=>18}], [:initialize, {:name=>"Jane", :age=>23}]]

tap_on!

tap_on!(object) - tracks any calls received by the object.

class PostsController < ApplicationController
  before_action :set_post, only: [:show, :edit, :update, :destroy]

  def show
    tap_on!(@post).and_print(:method_name_and_location)
  end
end

And you can see these in log:

name FROM /PROJECT_PATH/sample/app/views/posts/show.html.erb:5
user_id FROM /PROJECT_PATH/sample/app/views/posts/show.html.erb:10
to_param FROM /RUBY_PATH/gems/2.6.0/gems/actionpack-5.2.0/lib/action_dispatch/routing/route_set.rb:236

Also check the track_as_records option if you want to track ActiveRecord records.

tap_passed!

tap_passed!(target) tracks method calls that takes the target as its argument. This is particularly useful when debugging libraries. It saves your time from jumping between files and check which path the object will go.

class PostsController < ApplicationController
  # GET /posts/new
  def new
    @post = Post.new

    tap_passed!(@post) do |payload|
      puts(payload.passed_at(with_method_head: true))
    end
  end
end

Passed as 'record' in method ':polymorphic_mapping'
  > def polymorphic_mapping(record)
  at /Users/st0012/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/polymorphic_routes.rb:131
Passed as 'klass' in method ':get_method_for_class'
  > def get_method_for_class(klass)
  at /Users/st0012/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/polymorphic_routes.rb:269
Passed as 'record' in method ':handle_model'
  > def handle_model(record)
  at /Users/st0012/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/polymorphic_routes.rb:227
Passed as 'record_or_hash_or_array' in method ':polymorphic_method'
  > def self.polymorphic_method(recipient, record_or_hash_or_array, action, type, options)
  at /Users/st0012/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/actionpack-6.0.0/lib/action_dispatch/routing/polymorphic_routes.rb:139

tap_assoc!

tap_assoc!(activerecord_object) tracks association calls on a record, like post.comments

tap_assoc!(order).and_print(:method_name_and_location)

payments FROM /RUBY_PATH/gems/2.6.0/gems/jsonapi-resources-0.9.10/lib/jsonapi/resource.rb:124
line_items FROM /MY_PROJECT/app/models/line_item_container_helpers.rb:44
effective_line_items FROM /MY_PROJECT/app/models/line_item_container_helpers.rb:110
amending_orders FROM /MY_PROJECT/app/models/order.rb:385
amends_order FROM /MY_PROJECT/app/models/order.rb:432

tap_sql!

tap_sql!(anything_that_generates_sql_queries) tracks sql queries generated from the target

class PostsController < ApplicationController
  def index
    # simulate current_user
    @current_user = User.last
    # reusable ActiveRecord::Relation
    @posts = Post.all

    tap_sql!(@posts) do |payload|
      puts("Method: #{payload[:method_name]} generated sql: #{payload[:sql]} from #{payload[:filepath]}:#{payload[:line_number]}")
    end
  end
end

<h1>Posts (<%= @posts.count %>)</h1>
......
  <% @posts.each do |post| %>
    ......
  <% end %>
......
<p>Posts created by you: <%= @posts.where(user: @current_user).count %></p>

Method: count generated sql: SELECT COUNT(*) FROM "posts" from /PROJECT_PATH/rails-6-sample/app/views/posts/index.html.erb:3
Method: each generated sql: SELECT "posts".* FROM "posts" from /PROJECT_PATH/rails-6-sample/app/views/posts/index.html.erb:16
Method: count generated sql: SELECT COUNT(*) FROM "posts" WHERE "posts"."user_id" = ? from /PROJECT_PATH/rails-6-sample/app/views/posts/index.html.erb:31