Question

I would like to make something like this:

@profiles
#(I think in Java, so I have declared an @profiles variable there! I know it's probably wrong!)
@users.each do |user|
  profile = Profile.find(params[user.id])
  @profiles.add(profile)
end

The user and profile have a one-to-one relationship.

user has one profile,
profile belongs to user

Answer 1

You need to initialize the array.

@profiles = []
@users.each do |user|
  profile = Profile.find(params[user.id])
  @profiles &lt&lt profile if profile
end

If you have a relationship, you should be able to just say:

@profiles = []
@users.each do |user|
  profile = user.profile
  @profiles &lt&lt profile if profile
end