Rails ActiveRecord .where方法不执行SQL查询

Question

I've written a set of Rails search methods that takes an optional parameter to define the rigor of the search. The core method is as follows:

class Participant < ActiveRecord::Base

  def self.matches(field_name, param, rigor = 'exact')
    where("lower(#{field_name}) like ?", "#{param}") if rigor == 'exact'
    where("lower(#{field_name}) like ?", "%#{param}%") if rigor == 'soft'
  end

end

I'm getting this result:

[1] pry(main)> >> Participant.matches('last_name', 'Goodman', 'soft')
Participant.matches('last_name', 'Goodman', 'soft')
      Participant Load (5.1ms)  SELECT "participants".* FROM "participants" WHERE (lower(last_name) like '%Goodman%')
    => [#<Participant:0x007fc6fecee8d0
      id: 17,
      first_name: "Harris",
      last_name: "Goodman",
      gender: 0,
      birthdate: nil,
      city: nil,
      state_code: "CA",
      email: nil,
      phone: nil,
      created_at: Wed, 30 Mar 2016 11:18:33 MDT -06:00,
      updated_at: Wed, 30 Mar 2016 11:18:33 MDT -06:00,
      created_by: 1,
      updated_by: 1,
      country_code: "US",
      user_id: nil>]

    [2] pry(main)> >> Participant.matches('last_name', 'Goodman', 'exact')
    Participant.matches('last_name', 'Goodman', 'exact')
    => nil

Rails doesn't seem to be firing the SQL query when the 'exact' parameter is passed.

I've also tried = in place of like but get the same result. Worked on this for over an hour with no success. Any ideas would be welcome.

EDIT: OK, so a bit of refactoring solves the problem:

  def self.matches(field_name, param)
    where("lower(#{field_name}) like ?", "%#{param}%")
  end

  def self.exact_matches(field_name, param)
    where("lower(#{field_name}) like ?", "#{param}")
  end

I would still like to know why this works but the more elegant earlier solution does not.

Answer 1

Every function/method returns the last evaluated value. In your case it's where("lower(#{field_name}) like ?", "%#{param}%") if rigor == 'soft'

which returns nil if rigor is not 'soft'. So adding a return should doing what you want:

 def self.matches(field_name, param, rigor = 'exact')
    return where("lower(#{field_name}) like ?", "#{param}") if rigor == 'exact'
    where("lower(#{field_name}) like ?", "%#{param}%") if rigor == 'soft'
  end