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diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 74cd9bdc7b..c272daac28 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -16,7 +16,7 @@ After reading this guide, you will know: Why Associations? ----------------- -Why do we need associations between models? Because they make common operations simpler and easier in your code. For example, consider a simple Rails application that includes a model for customers and a model for orders. Each customer can have many orders. Without associations, the model declarations would look like this: +In Rails, an _association_ is a connection between two Active Record models. Why do we need associations between models? Because they make common operations simpler and easier in your code. For example, consider a simple Rails application that includes a model for customers and a model for orders. Each customer can have many orders. Without associations, the model declarations would look like this: ```ruby class Customer < ActiveRecord::Base @@ -71,7 +71,7 @@ To learn more about the different types of associations, read the next section o The Types of Associations ------------------------- -In Rails, an _association_ is a connection between two Active Record models. Associations are implemented using macro-style calls, so that you can declaratively add features to your models. For example, by declaring that one model `belongs_to` another, you instruct Rails to maintain Primary Key-Foreign Key information between instances of the two models, and you also get a number of utility methods added to your model. Rails supports six types of associations: +Rails supports six types of associations: * `belongs_to` * `has_one` @@ -80,6 +80,8 @@ In Rails, an _association_ is a connection between two Active Record models. Ass * `has_one :through` * `has_and_belongs_to_many` +Associations are implemented using macro-style calls, so that you can declaratively add features to your models. For example, by declaring that one model `belongs_to` another, you instruct Rails to maintain [Primary Key](https://en.wikipedia.org/wiki/Unique_key)-[Foreign Key](https://en.wikipedia.org/wiki/Foreign_key) information between instances of the two models, and you also get a number of utility methods added to your model. + In the remainder of this guide, you'll learn how to declare and use the various forms of associations. But first, a quick introduction to the situations where each association type is appropriate. ### The `belongs_to` Association @@ -238,13 +240,15 @@ class CreateAppointments < ActiveRecord::Migration end ``` -The collection of join models can be managed via the API. For example, if you assign +The collection of join models can be managed via the [`has_many` association methods](#has-many-association-reference). +For example, if you assign: ```ruby physician.patients = patients ``` -new join models are created for newly associated objects, and if some are gone their rows are deleted. +Then new join models are automatically created for the newly associated objects. +If some that existed previously are now missing, then their join rows are automatically deleted. WARNING: Automatic deletion of join models is direct, no destroy callbacks are triggered. |