easiest way to check if an item is in `has_many` field of another model?

Question

I have 3 tables, cooler,cpu,socket. A cooler (supports/)has_many sockets and cpu belongs_to socket. Now I what is the easiest way to check if cooler supports cpu or not?

@cooler.sockets.include? @cpu.socket # => False always no matter what

I tried to check types using:

@cooler.sockets.class
#=> #Socket::ActiveRecord_Associations_CollectionProxy

Answer 1

Your code:

@cooler.sockets.include? @cpu.socket

always returns false, because here you are trying to check if Cpu's model instance socket attribute is contained in the array of Socket model instances corresponding to the Cooler model instance, and that can never possibly happen.

However, you can accomplish what you want with .exists?:

@cooler.sockets.exists?(socket: @cpu.socket)

or .present?:

@cooler.sockets.where(socket: @cpu.socket).present?

Answer 2

@suslov explained and gave couple of ways to solve your requirement. Here is one way, I can think of :

@cooler.sockets.where(socket: @cpu.socket).any?

Read the any? method.