Rails / Javascript：如何注入rails变量到（非常）简单的javascript [英] Rails/Javascript: How to inject rails variables into (very) simple javascript

问题描述

我想在rails中写一个非常简单的javascript计算器，它将输入字段的数量乘以存储在rails变量中的数字（@ item.base_price）

I want to write up a very simple javascript calculator in rails which multiplies the quantity of an input field by a number stored in a rails variable (@item.base_price)

因此，在javascript / coffeescript方面，这是粗略的：

So, on the javascript/coffeescript side of things, it's crudely this:

# app/assets/javascript/items.js.coffee
$ -> 
  $('#item_quantity').change ->
    quantity_val = $(this).val()
    $('#total_amount').html(quantity_val * <%= [e-mail]_PRICE_HERE %>)

我知道我怎么能通过ajax调用每个change（）调用，但我认为有

I'm aware of how I can do this via an ajax call on each change() call, but I figure there has to be an elegant, hopefully unobtrusive rails way which doesn't hit the server each time.

任何建议非常感谢

推荐答案

如果您使用rails 3.1，您可以利用资源管道对javascript文件进行一些预处理，然后再提供它们。为此，只需更改文件扩展名：

If you are using rails 3.1 you can take advantage of the assets pipeline to do some pre-processing on the javascript files before you serve them up. To do this just change the file extension from:

items.js.coffee

到

items.js.coffee.erb

那么你可以添加ruby到你的javascript，就像在你的视图中使用< ;％=％> 标记。你可能遇到的唯一的问题是，你的items.js文件将提供给每个请求任何应用程序的控制器方法。因此，最好编写一个只在实例变量初始化时返回值的辅助方法

then you can add ruby to your javascript just like in your view with <%= %> tags. The only gotcha you might run into, is that your items.js file will be served to every request to any of your app's controller methods. So its best to write a helper method that will return the value only if the instance variable is initialized

例如在items_helper.rb

For example in items_helper.rb

def item_price
    if @item
        @item.base_price
    else
        0
    end
end

编辑：更多关于资产管道的信息：

more about assets pipeline here:

http://guides.rubyonrails.org/asset_pipeline.html

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