Extended callbacks to allow a hook to be defined with a block, and th…

…en content can be appended or prepended, or replace or remove the block entirely. Is fully backwards compatible with existing view hooks

lib/fat_free_crm/callback.rb

@@ -38,19 +38,44 @@ def self.responder(method)
     # - array with multiple items returned by the hook chain.
     #--------------------------------------------------------------------------
     def self.hook(method, caller, context = {})
-      responder(method).inject([]) do |response, m|
-        response << m.send(method, caller, context)
+      responder(method).inject(Hash.new([])) do |response, m|
+        response[m.class.positions[method]] += [m.send(method, caller, context)]
+        response
       end
     end
 
     #--------------------------------------------------------------------------
     class Base
       include Singleton
-
       def self.inherited(child)
         FatFreeCRM::Callback.add(child)
+        # Positioning hash to determine where content is placed.
+        child.class_eval do
+          @positions = Hash.new(:after)
+        end
         super
       end
+
+      class << self
+        attr_accessor :positions
+
+        def insert_before(hook, &block)
+          define_method hook, &block
+          @positions[hook] = :before
+        end
+        def insert_after(hook, &block)
+          define_method hook, &block
+          @positions[hook] = :after
+        end
+        def replace(hook, &block)
+          define_method hook, &block
+          @positions[hook] = :replace
+        end
+        def remove(hook)
+          define_method hook, Proc.new{""}
+          @positions[hook] = :replace
+        end
+      end
 
     end # class Base
 
@@ -59,9 +84,33 @@ def self.inherited(child)
     # data otherwise.
     #--------------------------------------------------------------------------
     module Helper
-      def hook(method, caller, context = {})
-        data = FatFreeCRM::Callback.hook(method, caller, context)
-        caller.class.to_s.start_with?("ActionView") ? data.join : data
+      def hook(method, caller, context = {}, &block)
+        is_view_hook = caller.class.to_s.start_with?("ActionView")
+
+        # If a block was given, hooks can choose to replace, append or prepend view content.
+        if block and is_view_hook
+          hook_hash = FatFreeCRM::Callback.hook(method, caller, context)
+          # Add content to the view with the following logic:
+          # -- before
+          # -- replace || original block
+          # -- after
+          view_data = ""
+          hook_hash[:before].each{|data| view_data << data }
+          # Only render the original view block if there are no :replace operations
+          if hook_hash[:replace].empty?
+            view_data << capture(&block)
+          else
+            hook_hash[:replace].each{|data| view_data << data }
+          end
+          hook_hash[:after].each{|data| view_data << data }
+          view_data
+
+        # Else, if no was block given.. (for backwards compatibility with existing hooks)
+        else
+          # All legacy hooks will have data stored in the :after key.
+          data = FatFreeCRM::Callback.hook(method, caller, context)[:after]
+          is_view_hook ? data.join : data
+        end
       end
     end # module Helper
 

spec/lib/fat_free_crm/callback_spec.rb

@@ -0,0 +1,51 @@
+require File.expand_path(File.dirname(__FILE__) + '/../../spec_helper')
+
+class TestCallback < FatFreeCRM::Callback::Base
+  insert_before :test_before do |view, context|
+    "BEFORE-"
+  end
+  insert_after :test_after do |view, context|
+    "-AFTER"
+  end
+  replace :test_replace do |view, context|
+    "REPLACE"
+  end
+  remove :test_remove
+
+  def test_legacy(view, context={})
+    "LEGACY"
+  end
+end
+
+include FatFreeCRM::Callback::Helper
+include ActionView::Helpers::CaptureHelper
+
+def test_hook(position)
+  Haml::Engine.new(%Q^
+= hook("test_#{position}".to_sym, ActionView::Base.new) do
+  BLOCK^).render.gsub("\n",'')
+end
+
+describe FatFreeCRM::Callback do 
+  it "should insert content before the block" do
+    test_hook(:before).should == "BEFORE-BLOCK"
+  end
+
+  it "should insert content after the block" do
+    test_hook(:after).should == "BLOCK-AFTER"
+  end
+
+  it "should replace the content of the block" do
+    test_hook(:replace).should == "REPLACE"
+  end
+
+  it "should remove the block" do
+    test_hook(:remove).should == ""
+  end
+
+  it "should still work for legacy hooks" do
+  Haml::Engine.new(%Q^
+= hook(:test_legacy, ActionView::Base.new)
+  ^).render.gsub("\n",'').should == "LEGACY"
+  end
+end