#23 FromArray.map implemented and tested

lib/fromarray.rb

@@ -53,6 +53,23 @@ def filter(&condition)
       FromArray.new(filtered)
     end
 
+    # Map the stream's elements to a given value using a function.
+    # Example (map int to string):
+    #
+    # stream = Stream::FromArray.new([1, 2, 3])
+    # collected = stream.map {|num| num.to_s}.collect
+    # puts collected # ['1', '2', '3']
+    #
+    # +function+:: Ruby Block function taking one parameter
+    #              (the element in the stream).
+    def map(&function)
+      mapped = []
+      @array.each do |val|
+        mapped.push(function.call(val))
+      end
+      FromArray.new(mapped)
+    end
+
     # Skip the first n elements of the stream.
     # +count+:: Number of elements to skip from the beginning of the stream.
     def skip(count)

test/fromarray_test.rb

@@ -128,7 +128,7 @@ def test_skips_all_elements_count_gt_size
     # condition.
     def test_filter_elements
       stream = FromArray.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
-      collected = stream.filter {|num| num % 2 == 0}.collect
+      collected = stream.filter { |num| num % 2 == 0 }.collect
       collected.each do |val|
         assert(val.even?)
       end
@@ -138,15 +138,15 @@ def test_filter_elements
     # the condition.
     def test_filters_no_elements
       stream = FromArray.new([2, 4, 6, 8])
-      collected = stream.filter {|num| num % 2 == 0}.collect
+      collected = stream.filter { |num| num % 2 == 0 }.collect
       assert(stream.collect == collected)
     end
 
     # FromArray filters out all elements because none of are satisfying
     # the condition.
     def test_filters_all_elements
       stream = FromArray.new([2, 4, 6, 8])
-      assert(stream.filter {|num| num % 2 != 0}.count == 0)
+      assert(stream.filter { |num| num % 2 != 0 }.count == 0)
     end
 
     # Filtering a stream should return a new instance rather than modifying
@@ -156,5 +156,30 @@ def test_filter_returns_new_instance
       assert(!stream.filter(&:odd?).equal?(stream))
       assert(stream.collect == [2, 4, 6, 8])
     end
+
+    # FromArray can map its elements using a given function.
+    def test_map_elements
+      stream = FromArray.new([1, 2, 3])
+      strings = stream.map { |num| num.to_s }.collect
+      strings.each do |val|
+        assert(val.is_a?(String))
+      end
+    end
+
+    # FromArray can map its single element.
+    def test_maps_one_element
+      stream = FromArray.new([1])
+      strings = stream.map { |num| num.to_s }.collect
+      strings.each do |val|
+        assert(val.is_a?(String))
+      end
+    end
+
+    # FromArray.map works when the stream is empty.
+    def test_maps_no_elements
+      stream = FromArray.new([])
+      collected = stream.map { |val| val.to_s }.collect
+      assert(collected.empty?)
+    end
   end
 end