Rails 3 ActiveRecord API: .build method

Question

I am fairly new to Ruby/RoR (outside of a year) and I have noticed that there are several different methods inside of RoR or Ruby that basically do the same thing. The one method I am wanting to get some sort of clarification on, is the .build method. when it is effective to use or how to use it in its best light, sorta thing.

Thanks!

Is it simply just a collection of items associated to the instantiated model? For ex: `Firm.clients.build(1)`... this would return all clients associated to the `Firm where firm_id = 1` — dennismonsewicz, Aug 22 '11 at 19:34
see http://stackoverflow.com/questions/4954313/build-vs-new-in-rails-3 — Doon, Aug 22 '11 at 19:46

score 5 · Answer 1 · answered Mar 17 '13 at 20:15

The .build method is an ActiveRecord method which is used to create a new record based on the has_many relationship in your model.

So lets say;

User has_many tweets

Then you can use

user.tweets.build(tweet_id)

This will create a new tweet in the tweets table associated with that user. It will also return that object too.

You probably want to put a params tweet_id in you argument depending on how you are implementing the app. :)

Rails 3 ActiveRecord API: .build method

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