来自多态模型的图像不显示

Question

I have a model named Hen:

class Hen < ApplicationRecord
  has_many :pictures, as: :imageable
  validates :name, :description, presence: true
end 

I added the :picture to whitelisted params in the HensController as well

Picture model:

class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
  has_attached_file :image
end

When creating new Hen, I can check that the instance is created. In console Hen.last.pictures returns

[["imageable_id", 3], ["imageable_type", "Hen"], ["LIMIT", 11]] => #

,so I assume that it is fine there. ... but I do not know how to dispay it in the view section. After some tries I have done that:

<p><%= @hen.pictures do |pic|  %></p>
  <%= image_tag pic.url %>
<% end %>

It dispays

#<Picture::ActiveRecord_Associations_CollectionProxy:0x00005640044034f0>* 

because I left the "=" there (to check if there is any object inside), but the picture is not displayed. I checked some other variants like pic.image_url and nothing works for me. Other images on the page display without problems. Console returns status 200:

Processing by HensController#show as HTML
  Parameters: {"id"=>"3"}
  User Load (0.6ms)  SELECT "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 1], ["LIMIT", 1]]
  Hen Load (0.5ms)  SELECT "hens".* FROM "hens" WHERE "hens"."id" = $1 LIMIT $2  [["id", 3], ["LIMIT", 1]]
  ↳ app/controllers/hens_controller.rb:16:in `show'
  Rendering hens/show.html.erb within layouts/application
  Rendered hens/show.html.erb within layouts/application (Duration: 5.9ms | Allocations: 3302)
[Webpacker] Everything's up-to-date. Nothing to do
Completed 200 OK in 125ms (Views: 67.7ms | ActiveRecord: 10.7ms | Allocations: 36995)*

Answer 1

You're not actually looping through pictures. You need to use @hen.picutres.each or for picture in @hen.pictures . Without this, you're just passing a block to @hen.pictures ; the block gets ignored and the expression returns @hen.pictures ( Picture::ActiveRecord_Associations_CollectionProxy ).

The equivalent plain-ruby would be

@hen.pictures { ... this block isn't used but it's not a syntax error ... }

instead of

@hen.pictures.each { |picture| ... this block is used by the `each` method }

Answer 2

Here <%= @hen.pictures do |pic|%> you are printing the picture url. you should not include = when you are looping <%= @hen %> wrong you should use <% @hen %> then you need to loop the pictures using each.

<% @hen.pictures.each do |pic| %>
  <%= image_tag pic.url %>
<% end %>

if the picture url in hash try to convert it into string using .to_s

<%= image_tag pic.url.to_s %>

Answer 3

This may not be the direct answer for the problem, but I found that better option is to use ActiveStorage than creating Polymorphic associations between models.

First, install the ActiveStorage:

rails active_storage:install

then add macro has_one_attached or has_many_attached to the models:

class Hen < ApplicationRecord
  has_one_attached :image
  validates :name, :description, presence: true
end 

add to the view form:

<%= f.file_field :image %>

whitelist the :image attribute:

def hens_params
  params.require(:hen).permit(:name, :description, :image)                                                           
end

Done.

To dispay the image in views:

<%= image_tag hen.image if hen.image.attached? %>

No need to create new model or to nest attributes.