Rails - Name can't be blank error when the input isn't blank - ruby-on-rails

Question

I get an error of 'Name can't be blank' and "Name only allows letters, numbers and '-'" when trying to update a name. This was working fine but I have just gone through it again while writing a test for it and realise it isn't working anymore, I can't figure out why or what has changed to break it.
Categories controller
def update
if #category.update category_params
redirect_to new_guide_category_item_path(#guide, #category)
flash[:info] = "Updated successfully"
else
render 'edit'
end
end
private
def category_params
params.require(:category).permit(:name, :template)
end
edit.html.erb
<%= render 'shared/error_messages', object: f.object %>
.....
<%= form_for([#guide, #category], url: guide_category_path) do |f| %>
<%= f.label :name, "Category name" %>
<%= f.text_field :name %>
<%= f.label :template, "Template" %>
<%= f.text_area :template, { :id => 'edit' } %>
<%= f.submit "Save", :value => "Save Template" %>
<% end %>
model
validates :name, presence: true, length: { maximum: 255 }, uniqueness: { scope: :guide_id, case_sensitive: false },
exclusion: { in: %w( guide guides category categories item items page pages post posts tag tags key keys item key item keys item-key item-keys item_key item_keys mod moderator mods moderators admin admins), message: "%{value} cant be taken." },
format: { with: /\A[a-zA-Z0-9 -]+\z/, message: "only allows letters, numbers, spaces and '-'" }
routes
resources :guides do
resources :categories, only: [:new, :create, :edit, :update] do
end
end
Anyone have an idea of what might be going wrong?
Edit added log output
Started PATCH "/guides/ghj/categories/ijijij" for ::1 at 2016-02-11 14:08:04 +1100
Processing by CategoriesController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"IqiUJ8wF8ZY4t8f91+t4aOMc9xenx/F2beKjKs9GY7JzLD6ZgPYDY1ueC2s+OIDL+PjROVtMe2+GvgYdan1CDQ==", "category"=>{"name"=>"ijijijddd", "template"=>""}, "commit"=>"Save Template", "guide_id"=>"ghj", "id"=>"ijijij"}
[1m[35mUser Load (0.2ms)[0m SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 1]]
[1m[36mGuide Load (0.1ms)[0m [1mSELECT "guides".* FROM "guides" WHERE "guides"."slug" = ? ORDER BY "guides"."id" ASC LIMIT 1[0m [["slug", "ghj"]]
[1m[35mCategory Load (0.1ms)[0m SELECT "categories".* FROM "categories" WHERE "categories"."slug" = ? ORDER BY "categories"."id" ASC LIMIT 1 [["slug", "ijijij"]]
[1m[36m (0.1ms)[0m [1mSELECT "category_item_keys"."name" FROM "category_item_keys" WHERE "category_item_keys"."category_id" = ?[0m [["category_id", 6]]
[1m[35m (0.0ms)[0m SELECT "check_category_item_keys"."name" FROM "check_category_item_keys" WHERE "check_category_item_keys"."category_id" = ? [["category_id", 6]]
[1m[36m (0.1ms)[0m [1mSELECT "category_item_keys"."name" FROM "category_item_keys" WHERE "category_item_keys"."category_id" = ? AND "category_item_keys"."key_type" = ?[0m [["category_id", 6], ["key_type", 1]]
[1m[35m (0.0ms)[0m SELECT "category_item_keys"."name" FROM "category_item_keys" WHERE "category_item_keys"."category_id" = ? AND "category_item_keys"."key_type" = ? [["category_id", 6], ["key_type", 2]]
[1m[36m (0.1ms)[0m [1mSELECT "category_item_keys"."name" FROM "category_item_keys" WHERE "category_item_keys"."category_id" = ? AND "category_item_keys"."key_type" = ?[0m [["category_id", 6], ["key_type", 3]]
[1m[35mGameModsRelationship Exists (0.1ms)[0m SELECT 1 AS one FROM "game_mods_relationships" WHERE "game_mods_relationships"."user_id" = ? AND "game_mods_relationships"."category_id" = 3 LIMIT 1 [["user_id", 1]]
[1m[36m (0.1ms)[0m [1mbegin transaction[0m
[1m[35mCategoryItemKey Exists (0.1ms)[0m SELECT 1 AS one FROM "category_item_keys" WHERE ("category_item_keys"."name" IS NULL AND "category_item_keys"."guide_id" IS NULL) LIMIT 1
[1m[36mCategory Exists (0.1ms)[0m [1mSELECT 1 AS one FROM "categories" WHERE (LOWER("categories"."name") = LOWER('ijijijddd') AND "categories"."id" != 6 AND "categories"."guide_id" = 3) LIMIT 1[0m
[1m[35m (0.0ms)[0m rollback transaction
[1m[36mCACHE (0.0ms)[0m [1mSELECT 1 AS one FROM "game_mods_relationships" WHERE "game_mods_relationships"."user_id" = ? AND "game_mods_relationships"."category_id" = 3 LIMIT 1[0m [["user_id", 1]]
Rendered shared/_error_messages.html.erb (0.5ms)
Rendered categories/edit.html.erb within layouts/application (5.6ms)
Rendered layouts/_shim.html.erb (0.1ms)
Rendered layouts/_header.html.erb (0.7ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 157ms (Views: 145.1ms | ActiveRecord: 1.1ms)`

Answer 1

You need to add error_messages helper tag in the partial. That handles all error messages and show it properly.

Answer 2

It looks like your database has an existing record with the same name. Try inputting a unique name in. In your model, it is checking for :uniqueness.