How do you iterate over active record objects in Ruby On Rails?

Question

This question is quite simple but I have run into the problem a few times.

Let's say you do something like:

cars = Vehicle.find_by_num_wheels(4)

cars.each do |c|
  puts "#{c.inspect}"
end

This works fine if cars is an array but fails if there is only one car in the database. Obviously I could do something like "if !cars.length.nil?" or check some other way if the cars object is an array before calling .each, but that is a bit annoying to do every time.

Is there something similar to .each that handles this check for you? Or is there an easy way to force the query result into an array regardless of the size?

erik · Accepted Answer · 2009-06-10 15:53:14Z

12

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cars = Vehicle.find_all_by_num_wheels(4)

The dynamic find_by_ methods only return one element and you have to use find_all_by_ to return multiple.

answered Jun 10, 2009 at 15:53

erik

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Comments

Steve Madsen · Accepted Answer · 2009-06-10 15:54:01Z

2

If you always want all of the cars, you should use find_all instead:

cars = Vehicle.find_all_by_num_wheels(4)

You could also turn a single Vehicle into an array with:

cars = [cars] unless cars.respond_to?(:each)

answered Jun 10, 2009 at 15:54

Steve Madsen

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Comments

marcgg · Accepted Answer · 2009-06-10 16:56:10Z

1

You can do this to get arrays everytimes :

cars = Vehicle.find(:all, :conditions => {num_wheels => 4})

I don't think that you have a loop that will check if the object is an array.

Another solution could be:

for i in (1..cars.lenght)
  puts cars[i].inspect
end

(haven't tested, it might break to test the lenght on a string. Let me know if it does)

answered Jun 10, 2009 at 16:56

marcgg

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Comments

Subba Rao · Accepted Answer · 2009-06-11 14:07:45Z

1

Named scoped version for your problem

Vehicle.scoped(:conditions => { :num_wheels => 4 } ).each { |car| car.inspect }

edited Jun 11, 2009 at 14:07

answered Jun 10, 2009 at 23:02

Subba Rao

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1 Comment

Chuck Over a year ago

I think that would be an anonymous scope, seeing as how you didn't name it. Scopes are a good answer to this, though.

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