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Instance variables in Rails controllers

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Now let's try to display list of tasks from the database.

Open app/controllers/tasks_controller and let's change the index action:

1class TasksController < ApplicationController
2  def index
3    @tasks = Task.all
4  end
5end

Open app/views/tasks/index.html.erb file and let's pass @tasks:

1<% @tasks.each do |task| %>
2  <p>
3    <%= task.id %>
4    <%= task.title %>
5  </p>
6<% end %>

Now visit http://localhost:3000/tasks and we will see a list of tasks.

Note: You may have noticed we haven't added any import statements in TaskController and still we have access to the Task model. This is because we do not need to explicitly import modules in Rails due to to the concept of autoloading implemented in Rails. If you're curious to know more about the autoloading feature, then you can go through the Loading behaviour of Ruby on Rails in depth chapter which addresses this topic in detail and then come back to where you left.

Instance variables in view files

In the controller we set @tasks which is used in the view file. A variable set in Rails controller starting with @ sign are called instance variables.

The specialty of instance variables is that they're available in our Rails views. We don't need to pass them explicitly to our Rails views.

That's why in the index.html.erb we are able to refer to @tasks.

Any instance variable created in a controller is available in the view file.

If the variable in the controller is not an instance variable (all variables without @ sign are not instance variables) then those variable will not be available in the views.

Now let's commit these changes:

1git add -A
2git commit -m "Added instance variables in Tasks controller"