Add additional_context param to TitleHelper#title

The helper previously passed the view assigns to the PageTitle to be used in
internationalised strings. This commit allows the caller to pass a Hash
which will be merged into the view assigns, making it possible to use
additional values in page titles.

* Document additional context parameter in README.

README.md

@@ -35,6 +35,19 @@ def to_s
 end
 ```
 
+You can pass additional values to the `#title` helper, which can be referenced
+in your translations:
+
+```erb
+<title><%= title(user_name: current_user.name) %></title>
+```
+
+```yaml
+en:
+  titles:
+    application: '%{user_name} - AppName'
+```
+
 ## Acknowledgement
 
 Though the idea of translating titles was arrived at seperately, [Brandon

app/helpers/title/title_helper.rb

@@ -1,7 +1,8 @@
 module Title
   module TitleHelper
-    def title
-      PageTitle.new(controller_path, action_name, controller.view_assigns.symbolize_keys).to_s
+    def title(additional_context = {})
+      context = controller.view_assigns.merge(additional_context).symbolize_keys
+      PageTitle.new(controller_path, action_name, context).to_s
     end
 
     class PageTitle

spec/helpers/title_helper_spec.rb

@@ -37,15 +37,24 @@
     stub_rails
     stub_controller_and_action(:users, :show)
     load_translations(users: { show: '%{name}' })
-    helper.stub_chain(:controller, :view_assigns, :symbolize_keys).and_return({ name: 'Caleb' })
+    helper.stub_chain(:controller, :view_assigns).and_return('name' => 'Caleb')
 
     expect(helper.title).to eq('Caleb')
   end
 
+  it 'can accept a hash of extra context in addition to the view assigns' do
+    stub_rails
+    stub_controller_and_action(:users, :show)
+    load_translations(users: { show: '%{greeting} %{name}' })
+    helper.stub_chain(:controller, :view_assigns).and_return('name' => 'Caleb')
+
+    expect(helper.title(greeting: 'Hello')).to eq('Hello Caleb')
+  end
+
   def stub_rails
     helper.stub(:controller_path).and_return('dashboards')
     helper.stub(:action_name)
-    helper.stub_chain(:controller, :view_assigns, :symbolize_keys).and_return({})
+    helper.stub_chain(:controller, :view_assigns).and_return({})
     Rails.stub_chain(:application, :class).and_return('Dummy::Application')
   end