Add Invoking Rake Tasks Multiple Times as a ruby til.

README.md

@@ -118,6 +118,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)
 - [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
+- [Invoking Rake Tasks Multiple Times](ruby/invoking-rake-tasks-multiple-times.md)
 - [Last Raised Exception In The Call Stack](ruby/last-raised-exception-in-the-call-stack.md)
 - [Limit Split](ruby/limit-split.md)
 - [Listing Local Variables](ruby/listing-local-variables.md)

ruby/invoking-rake-tasks-multiple-times.md

@@ -0,0 +1,32 @@
+# Invoking Rake Tasks Multiple Times
+
+I have a rake task, `build`, that builds a single record for development
+purposes. I want a supplemental rake task, `build:all`, that builds a bunch
+of different records. To keep things dry, `build:all` should just invoke
+`build` a number of times.
+
+```ruby
+namespace :build do
+  task :all do
+    predefined_list.each do |data|
+      Rake::Task["build"].invoke(data)
+    end
+  end
+end
+```
+
+This doesn't work though. No matter how many items are in the list, the
+`build` task only seems to get run once. This is because by default tasks
+can only be invoked once in a given context. To get around this, the task
+needs to be reenabled after each invocation.
+
+```ruby
+namespace :build do
+  task :all do
+    predefined_list.each do |data|
+      Rake::Task["build"].invoke(data)
+      Rake::Task["build"].reenable
+    end
+  end
+end
+```