Squeel and rails… dynamic where clause

问题

Using Squeel, in a rails app, I have a hash of conditions:

{'trans' => 'manual'}

which i eventually plan on moving into an array... so i can also have an operator assignment.

[[field,operator,value][field,operator,value]]

I want to use a Model method, which for now i omit the operator and am I just trying == to get this to work... however, what i have below does not work.

def self.with_conditions(conditions)
    joins{car}.where do
      conditions.map {|key,value| (key==value) }.inject(:&)
    end
end

I also tried this:

def self.with_conditions(conditions)
  joins{car}.where do
    query = nil

    conditions.each do |key, value|
      q = (key == value)

      if query
        query &= q
      else
        query = q
      end
    end

    query     
  end
end

So, how do i get this to work with the ==, and then how would i eventually get this to work with a dynamic operator as well? thanks

In console, my SQL doesn't read in any of my conditions... for example:

in console:

> Timeslip.with_conditions({'car.year'=>'1991'})

SELECT "timeslips".* FROM "timeslips" INNER JOIN "cars" ON "cars"."id" = "timeslips"."car_id"

回答1:

You need to programmatically build the Squeel query. For example:

def self.with_conditions(conditions)
  conditions.map do |col, str|
    Squeel::Nodes::Predicate.new(Squeel::Nodes::Stub.new(col), :matches, str) # (email.matches "user@example.com")
  end.inject do |t, expr|
    t & expr # joins each expression from the .map above with & - to be converted to AND in the sql
  end.tap do |block|
    return where{(block)} # pass the constructed expression to Squeel
  end
end

On my User::User model I can run

User::User.with_conditions({email: "user@example.com", first_name: "Deefour"}).to_sql

and I will get

SELECT "user_users".* FROM "user_users"  WHERE (("user_users"."email" LIKE 'user@example.com' AND "user_users"."first_name" LIKE 'Deefour'))

回答2:

I don't know if this helps, but I did it this way using this helper method:

  def query_for_matches(key, value)
    stub = Squeel::Nodes::Stub.new(key)
    Squeel::Nodes::Predicate.new(stub, :matches, "%#{value}%")
  end

You have a hash of parameters from a request of something:

  dynamic_params = {'username' => 'some_name', 'email' => 'email@example.com'}

Then I use this with a chain of where's in a loop:

  query = SomeModel #could be User, etc
  dynamic_params.each_pair {|key,value| query = query.where(query_for_matches(key, value)) }

You can then pass query to your view or whatever. I've only been on rails for a couple of weeks so I'm not sure if this is a best practice but it works.

来源：https://stackoverflow.com/questions/14654010/squeel-and-rails-dynamic-where-clause

标签

ruby-on-rails

ruby-on-rails-3

squeel