How do you access an object's (ActiveRecord::Relation) value by key in Ruby on Rails?

Question

tl;dr How do I get the corresponding value with the key of an object?

I'm confused why

Atag.where(tag:'brand') gives me what I would call an object for lack of a better term: #<ActiveRecord::Relation [#<Atag id: 1, tag: "brand", created_at: "2015-01-31 04:29:20", updated_at: "2015-01-31 04:29:20">]>

But I'm having the basic difficult of accessing the corresponding value for the key :id.

Atag.where(tag:'brand').id and Atag.where(tag:'brand')[:id] and Atag.where(tag:'brand')(:id) all throw errors, while in this case I'm just trying to have the integer 1 returned.

I seem to be unable to ruby, nor find a succinct answer to this basic question with my google searching skills (or lack there of).

Thanks

Answer 1

Get the id of your tag = 'brand' with following query:

Atag.find_by(tag:'brand').id 

Check following variations:

Atag.find(1) 
#gives you the object with the Atag id = 1

Atag.find(100) #let's say this record does not exist then you will 
get ActiveRecord::RecordNotFound exception. 

Better option :

Atag.where(id: 1) 
#this returns you a relation and it's true you are trying to access
 only a single object.

Hence, you just need to modify it to :
Atag.where(id: 1).first 
#Above one will give you an object of Atag not an association result.
# to verfiy you can execute, Atag.where(id: 1).first.class

Atag.where(id: 999).first
 # In this case if there is no record found with id = 999, then it'll 
return  nil which can be easily handled than an exception found 
while using find method.

Get the same flavor using the dynamic finders.

Atag.find_by(id: 1) #gives the Atag with id 1 
Atag.find_by_id(1). # same as above.
Atag.find_by(id: 999) #if not found then simply returns nil. 
Atag.find_by(name: 'ruby') #return Atag object with name: 'ruby'
Atag.find_by_name('ruby') #same as above.