Rails - 如何删除散列中的最后一个逗号

Question

我各有一个 :

{
  "type": "FeatureCollection",
  "features": [
   <% @pois.each do |poi| %>
   {
    "type": "Feature",
    "geometry": {
      "type": "Point",
      "coordinates": [<%= poi.longitude %>, <%= poi.latitude %> ]
   },
 <% end %>
 ]
}

我想删除最后一次迭代的最后一个逗号。我该怎么办？

这不是 json，而是 Geojson。

我想要这样的东西:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
      "type": "Point",
      "coordinates": [2.484957, 44.6044089 ]
      },
      "properties": {}
    },
    {
      "type": "Feature",
      "geometry": {
      "type": "Point",
      "coordinates": [2.3749903, 44.5656783 ]
      },
     "properties": {}
    }
  ]
}

没关系，我只想删除最后一个逗号;)

Answer 1

我假设您正在尝试 create/edit 某种 JSON 对象。

您不应该 以这种方式处理JSON 对象。而是使用 ActiveModel::Serializers

来自ActiveModel::Serializers

user = User.find(1)
user.as_json
# => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#     "created_at" => "2006/08/01", "awesome" => true}

ActiveRecord::Base.include_root_in_json = true

user.as_json
# => { "user" => { "id" => 1, "name" => "Konata Izumi", "age" => 16,
#                  "created_at" => "2006/08/01", "awesome" => true } }

Answer 2

由于您可能对将一个数组转换为另一个数组感兴趣，因此可以使用 map 而不是 each，即

{
  "type": "FeatureCollection",
  "features": 
   <% @pois.map do |poi| %>
     {
       "type": "Feature",
       "geometry": {
         "type": "Point",
         "coordinates": [<%= poi.longitude %>, <%= poi.latitude %> ]
       }
     }
   <% end %>
}

Rails - 如何删除散列中的最后一个逗号

Rails - How to remove the last comma in a hash

ruby-on-rails

geojson