How to do a boolean operation on a set of records using/via ActiveRecord?-CodePudding

I have a task to determine if all boolean attributes of a subset of records are true. After using sum, I expected to have a similar method to work with booleans. However, I could not find such a thing.

I feel that there is a big chance that the answer is very clear, straightforward and available via a simple Google search, but I am not able to think of the correct phrases to search for it.

Example of what I am trying to achieve:

[
  #<User id: 1, name: "John", arborist: true>,
  #<User id: 2, name: "Ben", arborist: true>,
  #<User id: 3, name: "Betty", arborist: false>,
]

Should return false

[
  #<User id: 1, name: "John", arborist: true>,
  #<User id: 2, name: "Ben", arborist: true>,
  #<User id: 3, name: "Betty", arborist: true>,
]

Should return true

At the moment I am using count.

all_arborists? = ( User.count == User.where(arborist: true).count )

It gets me the result, but I feel there is more to it than my mind can figure out.

CodePudding user response：

You can simply check if there is a single non-arborist in the database:

all_arborists = !User.exists?(arborist: false)

You can defined it as a class method, rails magic will make it available on all scopes:

class User
  def self.all_arborists?
    !exists?(arborist: false)
  end
end

User.where(some_condition: foo).all_arborists?

CodePudding user response：

If you already have the records loaded in memory, and you're working with an Array, you can use Ruby's #all? method:

all_arborists = records.all? { |r| r.arborist }

If the records are in the DB and you don't want to load them in memory, then you need a SQL query, and what you tried is on the right path:

non_arborists = User.where(some_condition: foo).where(arborist: false).count
all_arborists = non_arborists == 0