7600aef48b
As a side benefit, fix an (non-user-visible) bug in display_s5(). Also fixed a bug where removing orphaned pages did not expire cached summary pages.
104 lines
3.6 KiB
Plaintext
104 lines
3.6 KiB
Plaintext
== Add a `to_squawk` method to String ==
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To update a core class you will have to:
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* Write tests for the desired functionality.
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* Create a file for the code you wish to use.
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* Require that file from your 'init.rb'.
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Most plugins store their code classes in the plugin's lib directory. When you add a file to the lib directory, you must also require that file from 'init.rb'. The file you are going to add for this tutorial is 'lib/core_ext.rb'.
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First, you need to write the tests. Testing plugins is very similar to testing rails apps. The generated test file should look something like this:
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[source, ruby]
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--------------------------------------------------------
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# File: vendor/plugins/yaffle/test/core_ext_test.rb
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require 'test/unit'
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class CoreExtTest < Test::Unit::TestCase
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# Replace this with your real tests.
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def test_this_plugin
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flunk
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end
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end
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--------------------------------------------------------
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Start off by removing the default test, and adding a require statement for your test helper.
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[source, ruby]
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--------------------------------------------------------
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# File: vendor/plugins/yaffle/test/core_ext_test.rb
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require 'test/unit'
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require File.dirname(__FILE__) + '/test_helper.rb'
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class CoreExtTest < Test::Unit::TestCase
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end
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--------------------------------------------------------
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Navigate to your plugin directory and run `rake test`:
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--------------------------------------------------------
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cd vendor/plugins/yaffle
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rake test
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--------------------------------------------------------
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Your test should fail with `no such file to load -- ./test/../lib/core_ext.rb (LoadError)` because we haven't created any file yet. Create the file 'lib/core_ext.rb' and re-run the tests. You should see a different error message:
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--------------------------------------------------------
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1.) Failure ...
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No tests were specified
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--------------------------------------------------------
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Great - now you are ready to start development. The first thing we'll do is to add a method to String called `to_squawk` which will prefix the string with the word ``squawk!''. The test will look something like this:
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[source, ruby]
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--------------------------------------------------------
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# File: vendor/plugins/yaffle/init.rb
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class CoreExtTest < Test::Unit::TestCase
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def test_string_should_respond_to_squawk
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assert_equal true, "".respond_to?(:to_squawk)
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end
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def test_string_prepend_empty_strings_with_the_word_squawk
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assert_equal "squawk!", "".to_squawk
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end
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def test_string_prepend_non_empty_strings_with_the_word_squawk
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assert_equal "squawk! Hello World", "Hello World".to_squawk
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end
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end
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--------------------------------------------------------
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[source, ruby]
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--------------------------------------------------------
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# File: vendor/plugins/yaffle/init.rb
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require "core_ext"
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--------------------------------------------------------
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[source, ruby]
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--------------------------------------------------------
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# File: vendor/plugins/yaffle/lib/core_ext.rb
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String.class_eval do
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def to_squawk
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"squawk! #{self}".strip
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end
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end
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--------------------------------------------------------
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When monkey-patching existing classes it's often better to use `class_eval` instead of opening the class directly.
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To test that your method does what it says it does, run the unit tests. To test this manually, fire up a console and start squawking:
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--------------------------------------------------------
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$ ./script/console
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>> "Hello World".to_squawk
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=> "squawk! Hello World"
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--------------------------------------------------------
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If that worked, congratulations! You just created your first test-driven plugin that extends a core ruby class.
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