Setup cancancan that user couldn't destroy itself - ruby-on-rails

Question

I'm setting up cancancan to implement this function:
if the user is admin, it can destroy every user but himself.
This is my ability.rb
class Ability
include CanCan::Ability
def initialize(user)
if user.role == 'admin'
cannot :destroy, User, id: user.id
end
end
end
And here's my view
<h1>Listing Users</h1>
<table>
<thead>
<tr>
<th>E-Mail</th>
<th>Name</th>
<th>Role</th>
<th colspan="3"></th>
</tr>
</thead>
<tbody>
<% #users.each do |user| %>
<tr>
<td><%= user.email %></td>
<td><%= user.name %></td>
<td><%= user.role %></td>
<% if can? :destroy, #user %>
<%= link_to 'Destroy', user, method: :delete, data: { confirm: 'Are you sure?' } %>
<% end %>
</tr>
<% end %>
</tbody>
</table>
And even with this setup there's no destroy link at the end of every user now. What I want is that there's a destroy link behind every users but the admin himself. What should I do? Thanks!

Answer 1

Your main issue is that you're calling if can? :destroy, #user when #user doesn't exist:
<% #users.each do |user| %>
<% if can? :destroy, user %>
<% end %>
If the original answer does not work, perhaps you'd be better using a block to evaluate the user object:
#app/models/ability.rb
class Ability
include CanCan::Ability
def initialize(user)
user ||= User.new
case user.role
when "admin"
cannot :destroy, User do |x|
x.id == user.id
end
end
end
end
end
This will allow you to use:
<%= link_to 'Destroy', user, method: :delete, data: { confirm: 'Are you sure?' } if can? :destroy, user %>
... although fixing the first issue, I think, will resolve your issue.

Answer 2

Just because an admin cannot destroy itself, does not give it permission to destroy other users. You could try giving it destroy permissions.
class Ability
include CanCan::Ability
def initialize(user)
if user.role == 'admin'
cannot :destroy, User, id: user.id
else
can :destroy, User
end
end
end