[Rails][Route] Creating Paths and URLs From Objects

2.9 Creating Paths and URLs From Objects
In addition to using the routing helpers, Rails can also create paths and URLs from an array of parameters. For example, suppose you have this set of routes:

resources :magazines do
  resources :ads
end

When using magazine_ad_path, you can pass in instances of Magazine and Ad instead of the numeric IDs:

<%= link_to 'Ad details', magazine_ad_path(@magazine, @ad) %>

magazine_ad_pathに対して、IDを表す数値ではなく、オブジェクトを渡すことができる。

You can also use url_for with a set of objects, and Rails will automatically determine which route you want:

<%= link_to 'Ad details', url_for([@magazine, @ad]) %>

Magazine ModelとAd Modelと見なして、magazine_ad_pathを使用してくれる。

In this case, Rails will see that @magazine is a Magazine and @ad is an Ad and will therefore use the magazine_ad_path helper. In helpers like link_to, you can specify just the object in place of the full url_for call:

link_toメソッドなどのヘルパーでは、名前付きパスの部分にModelを渡してもいい。

<%= link_to 'Ad details', [@magazine, @ad] %>

If you wanted to link to just a magazine:

<%= link_to 'Magazine details', @magazine %>

For other actions, you just need to insert the action name as the first element of the array:

<%= link_to 'Edit Ad', [:edit, @magazine, @ad] %>

アクションを指定したいときは、配列の先頭要素として、アクション名を渡す。

This allows you to treat instances of your models as URLs, and is a key advantage to using the resourceful style.