Ruby on Rails的動態下拉列表（select_tag）

Question

我一直在嘗試創建3個動態下拉列表，第一個更改第二個內容，第二個更改第三個內容。

我還沒有找到一個這樣做的例子，我發現了一個例子，你將所有的信息發送到客戶端，並在那裏被過濾，但它不是我想要的。 我希望它在每次選擇發生變化時都與服務器進行交互。

如果有人有教程或可以給一個簡單的例子，我會很感激的是

感謝

Answer 1

你需要三樣東西，它的工作：

的Javascript上的改變事件對你的選擇：

// This will monitor your select control and start the process after its content has changed 
$('select#my_select_control').change(select_has_changed(this)); 

2-阿賈克斯的Javascript控制器功能：

// This will send the selected value to your Rails server 
function select_has_changed(obj) 
{ 
    // We get the selected value 
    var value = $(obj).val(); 

    // It's a good idea here to verify the value. 
    // For example if the value is empty we can empty the content 
    // of the target select control and do not go through ajax 

    // We make the ajax call to the rails controller 
    $.ajax({url: '/path/to/controller/action', 
      data: {value: value}, 
      // We are requesting for json response, but you can use html if you like 
      dataType: "json", 
      // Get method, or other is you like, you just have to 
      // define it accordingly in your routes 
      method: 'get' 
      // This is the function to call when ajax succeed 
      success: function (data) { fill_up_form(data, obj) } 
    }); 
} 

// This is called when Ajax was successful , and it will 
// fill up your target select control 
function fill_up_form(data, obj) 
{ 
    content = ... // Here you loop through your json data to create 
       // a set of OPTION tags 
       // Or if you used html as dataType, the rails server had it done 
       // so you can inject directly in your select target control 
    $('select#my_target_control').html(content); 
} 

3- Rails的控制器方法

# The action method that receive the ajax call 
# you must have set-up your routes accordingly 
def get_my_ajax_data 
    # This fetches the data from the database 
    # Note that we are using `params` with the same index as 
    # we used in the `data` hash of the ajax call 
    # which, in my example is `value` 
    records = Model.where(field: params[:value]) 

    # For a json request we return a collection of [id, text] 
    # that can be used to populate your target select control 
    # As an alternative we could have render a template if 
    # we was requesting for html content 
    render json: records.collect{ |r| {id: r.id, text: r.name} } 
end