Return array of IDs

Hi How can I return an array from a database call.

in this format: ["141", "138", "123", "128",开发者_开发问答 "137", "139"]

In Rails 4: (ht @ri4a)

User.ids # integer array
User.ids.map(&:to_s) # string array

In Rails 3/4:

User.pluck(:id) # integer array
User.pluck(:id).map(&:to_s) # string array

Old answer

If you want to go directly to the DB:

> ActiveRecord::Base.connection.select_values("select id from users")
["1", "2", "5", "6", "7", "8", "3", "10", "11", "9"]

If you already have a model:

User.all(:select => :id).collect(&:id)

First approach is faster than the 2nd as it does not incur the cost of constructing model instances.

If you have a has_many, then on the has_many side you can get the IDs for associated objects like this:

def User
  has_many :tasks
end

def Task
  belongs_to :user
end

ids = User.find(1).task_ids

How about:

ClassName.all.collect { |obj| obj.id }

If you use Model, there are new method - pluck. Comment.pluck(:id) #[1,2,3...]