Add a post install hook which allows a pod spec to run custom code.

For instance, by appending code to the Pods prefix header.

lib/cocoapods/installer.rb

 module Pod
-  # TODO the static library needs an extra xcconfig which sets the values from issue #1.
-  # Or we could edit the project.pbxproj file, but that seems like more work...
   class Installer
     include Config::Mixin
 
@@ -16,6 +14,10 @@ module Pod
       dependent_specification_sets.reject(&:only_part_of_other_pod?)
     end
 
+    def build_specifications
+      build_specification_sets.map(&:specification)
+    end
+
     def xcconfig
       @xcconfig ||= Xcode::Config.new({
         # In a workspace this is where the static library headers should be found
@@ -33,8 +35,7 @@ module Pod
     def generate_project
       puts "==> Generating Xcode project and xcconfig" unless config.silent?
       user_header_search_paths = []
-      build_specification_sets.each do |set|
-        spec = set.specification
+      build_specifications.each do |spec|
         xcconfig.merge!(spec.xcconfig)
         group = xcodeproj.add_pod_group(spec.name)
 
@@ -59,25 +60,22 @@ module Pod
     end
 
     def bridge_support_generator
-      BridgeSupportGenerator.new(build_specification_sets.map do |set|
-        set.specification.header_files.map do |header|
+      BridgeSupportGenerator.new(build_specifications.map do |spec|
+        spec.header_files.map do |header|
           config.project_pods_root + header
         end
       end.flatten)
     end
 
-    # TODO we need a spec that tests that all dependencies are first downloaded/installed
-    # before #generate_project is called!
     def install!
       puts "Installing dependencies of: #{@specification.defined_in_file}" unless config.silent?
-      build_specification_sets.each do |set|
-         set.specification.install!
-      end
+      build_specifications.each(&:install!)
       generate_project
       root = config.project_pods_root
       xcodeproj.create_in(root)
       xcconfig.create_in(root)
       bridge_support_generator.create_in(root) if @specification.generate_bridge_support
+      build_specifications.each(&:post_install)
     end
   end
 end

lib/cocoapods/specification.rb

@@ -257,8 +257,8 @@ module Pod
     # Override this if you need to perform work before or after activating the
     # pod. Eg:
     #
-    #   Pod::Spec.new do
-    #     def install!
+    #   Pod::Spec.new do |s|
+    #     def s.install!
     #       # pre-install
     #       super
     #       # post-install
@@ -290,8 +290,8 @@ module Pod
     # Override this if you need to perform work before or after downloading the
     # pod, or if you need to implement custom dowloading. Eg:
     #
-    #   Pod::Spec.new do
-    #     def download!
+    #   Pod::Spec.new do |s|
+    #     def s.download!
     #       # pre-download
     #       super # or custom downloading
     #       # post-download
@@ -303,6 +303,21 @@ module Pod
       downloader.clean(clean_paths) if config.clean
     end
 
+    # This is a convenience method which gets called after all pods have been
+    # downloaded, installed, and the Xcode project and related files have been
+    # generated. Override this to, for instance, add to the prefix header:
+    #
+    #   Pod::Spec.new do |s|
+    #     def s.post_install
+    #       prefix_header = config.project_pods_root + 'Pods-Prefix.pch'
+    #       prefix_header.open('a') do |file|
+    #         file.puts(%{#ifdef __OBJC__\n#import "SSToolkitDefines.h"\n#endif})
+    #       end
+    #     end
+    #   end
+    def post_install
+    end
+
   end
 
   Spec = Specification

spec/unit/installer_spec.rb

@@ -12,6 +12,21 @@ describe "Pod::Installer" do
     config.repos_dir = SpecHelper.tmp_repos_path
   end
 
+  it "generates a BridgeSupport metadata file from all the pod headers" do
+    spec = Pod::Spec.new do |s|
+      s.platform = :osx
+      s.dependency 'ASIHTTPRequest'
+    end
+    expected = []
+    installer = Pod::Installer.new(spec)
+    installer.build_specifications.each do |spec|
+      spec.header_files.each do |header|
+        expected << config.project_pods_root + header
+      end
+    end
+    installer.bridge_support_generator.headers.should == expected
+  end
+
   it "adds all source files that should be included in the library to the xcode project" do
     [
       [