require File.expand_path(File.dirname(__FILE__) + '/edgecase') class AboutIteration < EdgeCase::Koan def test_each_is_a_method_on_arrays [].methods.include?("each") end def test_iterating_with_each array = [1, 2, 3] sum = 0 array.each do |item| sum += item end assert_equal __, sum end def test_each_can_use_curly_brace_blocks_too array = [1, 2, 3] sum = 0 array.each { |item| sum += item } assert_equal __, sum end def test_break_works_with_each_style_iterations array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] sum = 0 array.each { |item| break if item > 3 sum += item } assert_equal __, sum end def test_collect_transforms_elements_of_an_array array = [1, 2, 3] new_array = array.collect { |item| item + 10 } assert_equal __, new_array # NOTE: 'map' is another name for the 'collect' operation another_array = array.map { |item| item + 10 } assert_equal __, another_array end def test_select_selects_certain_items_from_an_array array = [1, 2, 3, 4, 5, 6] even_numbers = array.select { |item| (item % 2) == 0 } assert_equal __, even_numbers # NOTE: 'find_all' is another name for the 'select' operation more_even_numbers = array.find_all { |item| (item % 2) == 0 } assert_equal __, more_even_numbers end def test_find_locates_the_first_element_matching_a_criteria array = ["Jim", "Bill", "Clarence", "Doug", "Eli"] assert_equal __, array.find { |item| item.size > 4 } end def test_inject_will_blow_your_mind result = [2, 3, 4].inject(0) { |sum, item| sum + item } assert_equal __, result result2 = [2, 3, 4].inject(1) { |sum, item| sum * item } assert_equal __, result2 # Extra Credit: # Describe in your own words what inject does. end def test_all_iteration_methods_work_on_any_collection_not_just_arrays # Ranges act like a collection result = (1..3).map { |item| item + 10 } assert_equal __, result # Files act like a collection of lines File.open("example_file.txt") do |file| upcase_lines = file.map { |line| line.strip.upcase } assert_equal __, upcase_lines end # NOTE: You can create your own collections that work with each, # map, select, etc. end # Bonus Question: In the previous koan, we saw the construct: # # File.open(filename) do |file| # # code to read 'file' # end # # Why did we do it that way instead of the following? # # file = File.open(filename) # # code to read 'file' # # When you get to the "AboutSandwichCode" koan, recheck your answer. end