Question

I have a set of resources called Tasks and Posts and there are in a has_and_belongs_to_many (HABTM) relationship with each other.

There is also a join table connecting their values.

create_table 'posts_tasks', :id => false do |t|
   t.column :post_id, :integer
   t.column :task_id, :integer
end

So my question is how do I check to see if the id of a specific task exists within the array created from @post.tasks?

irb(main):011:0> @post = Post.find(1)
=> #<Post id: 2, comment: "blah blah", created_at: "2011-10-18 03:40:30", updated_at:
irb(main):012:0> @post.tasks
=> [#<Task id: 1, description: "Test 1", created_at: "2011-10-18 03:
   22:05", updated_at: "2011-10-18 03:22:05">, #<Task id: 3, description: "Test 3",
   created_at: "2011-10-18 03:22:21", updated_at: "2011-10-18 03:22:21
    ">]

So my question is whats the ruby way for writing does “@task = Task.find(2)” exist within @post.tasks and if so return true or false?

Answer 1

@post.tasks.map(&:id).include?(task_id)

Where task_id is the id of the task you want to check. To explain this a little bit, you’re taking the list of tasks, mapping them to an array of their ids, and then checking to see if the id in question is in that array. If you’re not familiar with map you should check it out, it’s awesome.

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