Rails如何显示来自JSON请求的哈希

Question

我正在尝试从我的 JSON 请求中显示哈希的内部级别。

这是 JSON 请求的返回：

{
    "results": [
    {
    "utc_offset": -25200000,
    "venue": {
      "zip": "94305",
      "country": "us",
      "localized_country_name": "USA",
      "city": "Stanford",
      "address_1": "750 Escondido Road",
      "name": "Ray's - Graduate Community Center",
      "lon": -122.158386,
      "id": 5612552,
      "state": "CA",
      "lat": 37.423393,
      "repinned": false
    },
    "status": "upcoming"
    },
    {
    "utc_offset": -25200000,
    "venue": {
      "zip": "94306",
      "country": "us",
      "localized_country_name": "USA",
      "city": "Palo Alto",
      "address_1": "25 Churchill Ave",
      "name": "Palo Alto High School",
      "lon": -122.154121,
      "id": 1566333,
      "state": "CA",
      "lat": 37.433186,
      "repinned": false
    },
    "status": "upcoming"
    },
    {
    "utc_offset": -25200000,
    "venue": {
      "zip": "94306",
      "country": "us",
      "localized_country_name": "USA",
      "city": "Palo Alto",
      "address_1": "25 Churchill Ave",
      "name": "Palo Alto High School",
      "lon": -122.154121,
      "id": 1566333,
      "state": "CA",
      "lat": 37.433186,
      "repinned": false
    },
    "status": "upcoming"
    }
    ]
    }
}

我参考过：How to use JSON data returned by API call in Rails 4、How to get a second level field from json file using ruby、Why do I get "no implicit conversion of String into Integer (TypeError)"?、How to access JSON in Rails?

这有助于我达到这一点，如果我使用返回"Ray's - Graduate Community Center" 的@result = @api_response["results"][0]["venue"]["name"] 指定数组索引，我可以显示哈希的内部级别。这就是我要显示的内容，但我想显示列表中所有场地的名称，而不仅仅是索引 [0] 处的名称。但我不确定如何遍历索引。

我还可以使用@result = @api_response["results"] 显示散列结果并通过使用：

<% @result.each do |i| %>
  <%= i["venue"] %>
<% end %> 

返回：

{"zip"=>"94305", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Stanford", "address_1"=>"750 Escondido Road", "name"=>"Ray's - Graduate Community Center", "lon"=>-122.158386, "id"=>5612552, "state"=>"CA", "lat"=>37.423393, "repinned"=>false} 
{"zip"=>"94305", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Stanford", "address_1"=>"750 Escondido Road", "name"=>"Ray's - Graduate Community Center", "lon"=>-122.158386, "id"=>5612552, "state"=>"CA", "lat"=>37.423393, "repinned"=>false} 
{"zip"=>"94306", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Palo Alto", "address_1"=>"25 Churchill Ave", "name"=>"Palo Alto High School", "lon"=>-122.154121, "id"=>1566333, "state"=>"CA", "lat"=>37.433186, "repinned"=>false} 
{"zip"=>"94306", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Palo Alto", "address_1"=>"25 Churchill Ave", "name"=>"Palo Alto High School", "lon"=>-122.154121, "id"=>1566333, "state"=>"CA", "lat"=>37.433186, "repinned"=>false} 

{"zip"=>"94306", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Palo Alto", "address_1"=>"25 Churchill Ave", "name"=>"Palo Alto High School", "lon"=>-122.154121, "id"=>1566333, "state"=>"CA", "lat"=>37.433186, "repinned"=>false} 
{"zip"=>"94306", "country"=>"us", "localized_country_name"=>"USA", "city"=>"Palo Alto", "address_1"=>"25 Churchill Ave", "name"=>"Palo Alto High School", "lon"=>-122.154121, "id"=>1566333, "state"=>"CA", "lat"=>37.433186, "repinned"=>false} 

但是当我尝试使用这个时：

<% @result.each do |i| %>
  <%= i["venue"]["name"] %> <br />
<% end %> 

我收到 undefined method[]' 的 nil:NilClass` 错误，它不允许我访问我试图显示的“地点”内的“名称”。

我在正确的轨道上吗？有没有更好的方法来显示哈希的内部级别？任何反馈都会有所帮助。谢谢！

Answer 1

您确定results 数组中的每个对象都有venue 字段吗？

在尝试访问venue 字段之前，请确保查看该对象是否确实存在。在你的控制器中，添加这个

@result = @api_response["results"].reject {|obj| obj.nil?}

这将删除数组中的任何对象nil。

如果对象存在但venue 字段不存在怎么办？

<% @result.each do |i| %>
  <%= i.has_key? "venue" ? i["venue"]["name"] : 'Location unspecified' %> <br />
<% end %> 

如果这看起来很乱，你也可以把它移到一个辅助方法中，比如

def venue_name(obj)
  obj.has_key? "venue" ? obj["venue"]["name"] : 'Location unspecified'
end

然后在视图中使用它。

 <% @result.each do |i| %>
  <%= venue_name(i) %> <br/>
 <% end %> 

Answer 2

看起来你在正确的轨道上；只是那里有一个结果，要么是 nil，要么里面没有场地。

您如何解决问题取决于您想在这些情况下做什么。

您可以过滤结果以排除没有地点的结果。作为查询的一部分执行此操作会更有效，但您可以这样做：

@result.select { |r| r.present? && r.has_key?('venue') }.each do |i|

或者，如果场地丢失，您可以输出“无场地”或类似内容。在这种情况下，我倾向于使用fetch。您可以尝试从散列中获取值，但如果键不在散列中，则返回默认值。所以，在你的情况下，你可以这样做：

<%= i.fetch('venue', {}).fetch('name', 'No venue') %>

这会在结果中查找场地散列，但如果不存在则返回空散列。第二个fetch 然后尝试从该哈希中检索名称，如果找不到，则再次返回'No venue'。