触发：onchange事件时（红宝石在Rails 4上），如何调用ruby方法？

Question

I am pretty new to ruby on rails... On my _form.html.erb I have a collection_select field, which is populated from a Model called Product. The Product's table columns are id, name, and price . Once I select an item (product) from the collection I would like to populate a text field with the price of the selected product.

So far I have the following code IOT trigger an event when selecting an item:

<%= collection_select( :warehouse, :product_id, Product.all, :id, :name, {}, {:onchange => "alert('Hello World');"} )%>

How can I call a ruby method which would let me populate the text_field with the corresponding price for the selected product?

For the method I was thinking something like...

def set_price
      @price = Product.find(params[:id]).price
end

Answer 1

The erb snippet

<%= collection_select( :warehouse, :product_id, Product.all, :id, :name, {}, {:onchange => "alert('Hello World');"} )%>

generates the html snippet like this

<select name="warehouse[product_id]" onchange="alert('Hello World');">
  <option value="1">Product 1</option>
  <option value="2">Product 2</option>
  ...
</select>

So the content of onchange is just a piece of javascript, which runs on browsers. There is no way to let onchange run ruby code directly. All you can do is send an AJAX request in onchange , and let your Rails application respond to that request.