koans/about_blocks.rb

   1 require File.expand_path(File.dirname(__FILE__) + '/edgecase')
   2
   3 class AboutBlocks < EdgeCase::Koan
   4   def method_with_block
   5     result = yield
   6     result
   7   end
   8
   9   def test_methods_can_take_blocks
  10     yielded_result = method_with_block { 1 + 2 }
  11     assert_equal __, yielded_result
  12   end
  13
  14   def test_blocks_can_be_defined_with_do_end_too
  15     yielded_result = method_with_block do 1 + 2 end
  16     assert_equal __, yielded_result
  17   end
  18
  19   # ------------------------------------------------------------------
  20
  21   def method_with_block_arguments
  22     yield("Jim")
  23   end
  24
  25   def test_blocks_can_take_arguments
  26     result = method_with_block_arguments do |argument|
  27       assert_equal __, argument
  28     end
  29   end
  30
  31   # ------------------------------------------------------------------
  32
  33   def many_yields
  34     yield(:peanut)
  35     yield(:butter)
  36     yield(:and)
  37     yield(:jelly)
  38   end
  39
  40   def test_methods_can_call_yield_many_times
  41     result = []
  42     many_yields { |item| result << item }
  43     assert_equal __, result
  44   end
  45
  46   # ------------------------------------------------------------------
  47
  48   def yield_tester
  49     if block_given?
  50       yield
  51     else
  52       :no_block
  53     end
  54   end
  55
  56   def test_methods_can_see_if_they_have_been_called_with_a_block
  57     assert_equal __, yield_tester { :with_block }
  58     assert_equal __, yield_tester
  59   end
  60
  61   # ------------------------------------------------------------------
  62
  63   def test_block_can_affect_variables_in_the_code_where_they_are_created
  64     value = :initial_value
  65     method_with_block { value = :modified_in_a_block }
  66     assert_equal __, value
  67   end
  68
  69   def test_blocks_can_be_assigned_to_variables_and_called_explicitly
  70     add_one = lambda { |n| n + 1 }
  71     assert_equal __, add_one.call(10)
  72
  73     # Alternative calling sequence
  74     assert_equal __, add_one[10]
  75   end
  76
  77   def test_stand_alone_blocks_can_be_passed_to_methods_expecting_blocks
  78     make_upper = lambda { |n| n.upcase }
  79     result = method_with_block_arguments(&make_upper)
  80     assert_equal __, result
  81   end
  82
  83   # ------------------------------------------------------------------
  84
  85   def method_with_explicit_block(&block)
  86     block.call(10)
  87   end
  88
  89   def test_methods_can_take_an_explicit_block_argument
  90     assert_equal __, method_with_explicit_block { |n| n * 2 }
  91
  92     add_one = lambda { |n| n + 1 }
  93     assert_equal __, method_with_explicit_block(&add_one)
  94   end
  95
  96 end