Routes on Rails application are failing - ruby-on-rails

Question

I'm taking an MOOC and the goal of this exercise is to add a new functionality to typo, where i can merge two articles together.
When I add the route to my new function merge to the routes.rb I'm losing the functionality to delete articles. I think something clashes here, but I have no idea what.
The original routes.rb:
%w{advanced cache categories comments content profiles feedback general pages
resources sidebar textfilters themes trackbacks users settings tags redirects seo post_types }.each do |i|
match "/admin/#{i}", :to => "admin/#{i}#index", :format => false
match "/admin/#{i}(/:action(/:id))", :to => "admin/#{i}", :action => nil, :id => nil, :format => false
end
This method in articles.rb creates the correct url for deleting
def delete_url
blog.url_for(:controller => "/admin/content", :action =>"destroy",:id => id)
end
correct url:
http://example.com/admin/content/destroy/7
If i follow this link i can successfully delete an article.
However, if I add the following before that to my routes.rb:
namespace "admin" do
resources :content do
post :merge, on: :member, as: :merge
end
end
The new merging functionality and forms are working fine, but the method delete_url now produces something like this:
http://example.com/admin/content/7
and if I follow a link created by this method i get:
Unknown action
The action 'show' could not be found for Admin::ContentController
Maybe I'm overwriting something? I can't figure out what's happening here and why this affects the delete action / route.
Thanks in advance!
EDIT: rake routes | grep content:
with the original routes.rb gives me:
admin_content /admin/content {:controller=>"admin/content", :action=>"index"}
/admin/content(/:action(/:id)) {:action=>nil, :id=>nil, :controller=>"admin/content"}
whereas my modified routes.rb produces
merge_admin_content POST /admin/content/:id/merge(.:format) {:action=>"merge", :controller=>"admin/content"}
admin_content_index GET /admin/content(.:format) {:action=>"index", :controller=>"admin/content"}
POST /admin/content(.:format) {:action=>"create", :controller=>"admin/content"}
new_admin_content GET /admin/content/new(.:format) {:action=>"new", :controller=>"admin/content"}
edit_admin_content GET /admin/content/:id/edit(.:format) {:action=>"edit", :controller=>"admin/content"}
admin_content GET /admin/content/:id(.:format) {:action=>"show", :controller=>"admin/content"}
PUT /admin/content/:id(.:format) {:action=>"update", :controller=>"admin/content"}
DELETE /admin/content/:id(.:format) {:action=>"destroy", :controller=>"admin/content"}
/admin/content {:controller=>"admin/content", :action=>"index"}
/admin/content(/:action(/:id)) {:action=>nil, :id=>nil, :controller=>"admin/content"}

Answer 1

Okay, thanks to #guitarman i worked through my routes code and found out I can add the following except:
namespace "admin" do
resources :content, except: [:index, :show, :update, :destroy, :edit, :new, :create] do
post :merge, on: :member, as: :merge
end
end
after that, the rake routes just shows the additional merge route I wanted and my destroy action works fine again.

Answer 2

Check rake routes command. I think there is a route /admin/content/:id which will be created by resources :content in the namespace "admin".
Your request to http://example.com/admin/content/7 will be catched be the defined route but I gess you have no show action in the controller.
Better:
namespace "admin" do
post "/content/:id/merge", to: "admin/content#merge", as: :merge
end
For more information about recources and the CRUD operations please see the rails routing guide.