如何在模型中获取对象的属性-Ruby on Rails

Question

How can I get the attribute first_name of an entity called Applicant when I'm in a different model called Billing. So far I am able to make it work however, what is returned is the object and not only the attribute.

The following is my code:

class Billing < ActiveRecord::Base
    def self.to_csv
        attributes=%w{tenant bill_type_dec total_amount created_at datetime_paid paid }
        CSV.generate(headers:true) do |csv|
            csv<<attributes
            all.each do |bill|
                csv <<attributes.map{|attr| bill.send(attr)}
            end
        end
    end

    def bill_type_dec
        if bill_type!=nil
            if bill_type==1
                "Water"
            else
                "Electricity"
            end
        else
            "#{description}"
        end
    end

    def tenant
        @applicants=Applicant.where(id: tenant_id)
        @applicants.each do |appli|
                "#{appli.first_name}"

        end
    end
end

Answer 1

You probably want to use .map instead of .each .

You can get all the names of the applicants in an array by doing this:

@applicants.map { |appli| appli.first_name }

#=> ['John', 'Mary']

As you can see, .each returns the array itself.

.map will return the array generated by executing the block.

Answer 2

Or use pluck and avoid creating the ruby objects

def tenant
  Applicant.where(id: tenant_id).pluck(:first_name)
end

BTW - I see you have a tenant_id, if that means you have a belongs_to :tenant on the Billing class, you will want to pick a different method name (maybe "tenant_first_names"). If this is the case, and tenant has_many :applicants you can do this:

def tenant_first_names
  tenant.applicants.pluck(:first_name)
end