Add record to a has_and_belongs_to_many relationship

ruby-on-rails has-and-belongs-to-many relationship

user = User.find(params[:id])promotion = Promotion.find(params[:promo_id])user.promotions << promotion

user.promotions is an array of the promotions tied to the user.

See the apidock for all the different functions you have available.

ruby-on-rails has-and-belongs-to-many relationship

You can do just

User.promotions = promotion #notice that this will delete any existing promotions

User.promotions << promotion

You can read about has_and_belongs_to_many relationship here.

ruby-on-rails has-and-belongs-to-many relationship

This is also useful

User.promotion.build(attr = {})

so, promotion object saves, when you save User object.

And this is

User.promotion.create(attr = {})

create promotion you not need to save it or User model

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