followed srp principle.

bike.rb

@@ -1,39 +1,21 @@
 # Bike
+require_relative 'bike_cargo'
 
 class Bike
-
   STANDARD_WEIGHT = 200 # lbs
-  MAX_CARGO_ITEMS = 10
 
-  attr_accessor :id, :color, :price, :weight, :rented, :cargo_contents
+  attr_accessor :id, :color, :price, :weight, :rented, :cargo_contents, :bike_cargo
 
   def initialize(id, color, price, weight = STANDARD_WEIGHT, rented = false)
     @id = id
     @color = color
     @price = price
     @weight = weight
     @rented = rented
-    @cargo_contents = []
+    @bike_cargo = BikeCargo.new
   end
 
   def rent!
     self.rented = true
-  end
-
-  def add_cargo(item)
-    self.cargo_contents << item
-  end
-
-  def remove_cargo(item)
-    self.cargo_contents.remove(item)
-  end
-
-  def pannier_capacity
-    MAX_CARGO_ITEMS
-  end
-
-  def pannier_remaining_capacity
-    MAX_CARGO_ITEMS - self.cargo_contents.size
-  end
-
+  end 
 end

bike_cargo.rb

@@ -0,0 +1,27 @@
+class BikeCargo
+  MAX_CARGO_ITEMS = 10
+
+  attr_accessor :cargo_contents
+
+  def initialize
+    @cargo_contents = []
+  end
+
+  def add_cargo(item)
+    if pannier_remaining_capacity > 0
+      @cargo_contents << item
+    end
+  end
+
+  def remove_cargo(item)
+    @cargo_contents.remove(item)
+  end
+
+  def pannier_capacity
+    MAX_CARGO_ITEMS
+  end
+
+  def pannier_remaining_capacity
+    MAX_CARGO_ITEMS - @cargo_contents.size
+  end
+end

main.rb

@@ -1,13 +1,14 @@
-!# /usr/bin/env ruby
+# /usr/bin/env ruby
 
 require_relative 'bike'
+require_relative 'bike_cargo'
 
 bike = Bike.new(1, :pink, 99.99)
 
-bike.add_cargo(:apples)
-bike.add_cargo(:water)
-bike.add_cargo(:repair_kit)
+bike.bike_cargo.add_cargo(:apples)
+bike.bike_cargo.add_cargo(:water)
+bike.bike_cargo.add_cargo(:repair_kit)
 
-puts "Space for #{bike.pannier_remaining_capacity} items left."
+puts "Space for #{bike.bike_cargo.pannier_remaining_capacity} items left."
 
 bike.rent!