How to select where ID in Array Rails ActiveRecord without exception

If it is just avoiding the exception you are worried about, the "find_all_by.." family of functions works without throwing exceptions.

Comment.find_all_by_id([2, 3, 5])

will work even if some of the ids don't exist. This works in the

user.comments.find_all_by_id(potentially_nonexistent_ids)

case as well.

Update: Rails 4

Comment.where(id: [2, 3, 5])

Update: This answer is more relevant for Rails 4.x

Do this:

current_user.comments.where(:id=>[123,"456","Michael Jackson"])

The stronger side of this approach is that it returns a Relation object, to which you can join more .where clauses, .limit clauses, etc., which is very helpful. It also allows non-existent IDs without throwing exceptions.

The newer Ruby syntax would be:

current_user.comments.where(id: [123, "456", "Michael Jackson"])

If you need more control (perhaps you need to state the table name) you can also do the following:

Model.joins(:another_model_table_name)
  .where('another_model_table_name.id IN (?)', your_id_array)

Now .find and .find_by_id methods are deprecated in rails 4. So instead we can use below:

Comment.where(id: [2, 3, 5])

It will work even if some of the ids don't exist. This works in the

user.comments.where(id: avoided_ids_array)

Also for excluding ID's

Comment.where.not(id: [2, 3, 5])

To avoid exceptions killing your app you should catch those exceptions and treat them the way you wish, defining the behavior for you app on those situations where the id is not found.

begin
  current_user.comments.find(ids)
rescue
  #do something in case of exception found
end

Here's more info on exceptions in ruby.

You can also use it in named_scope if You want to put there others conditions

for example include some other model:

named_scope 'get_by_ids', lambda { |ids| { :include => [:comments], :conditions => ["comments.id IN (?)", ids] } }