Group 2

Homeworks/Answer.md

@@ -0,0 +1,176 @@
+#Clean-code
+#1
+#smell code example (Duplicate Method)
+class student
+  def checkpoint point
+    if point.max < 3
+      puts "week"
+    else point.max >= 5
+      puts "normal"
+    end
+  end
+end
+#refactor
+class student
+  def checkpoint point
+      max_point = point.max
+    if max_point < 3
+      puts "week"
+    else max_point >= 5
+      puts "normal"
+    end
+  end
+end
+#2
+#smell code example( If ___ Return True, Else Return False)
+class Animal
+  attr_reader :type
+
+  def initialize type
+    @type = type
+  end
+
+  def is_a_dog?
+    if @type == "dog"
+      return true
+    else
+      return false
+    end
+  end
+end
+#refactor
+class Animal
+  attr_reader :type
+
+  def initialize type
+    @type = type
+  end
+
+  def is_a_dog?
+    @type == "dog"
+  end
+end
+#3
+
+class Language
+  def speak name
+    case name
+    when "english"
+      puts "hello, english"
+    when "chinese"
+      puts "hello, chinese"
+    when "Vietnam"
+      puts "xin chao, Viet Nam"
+    else
+      puts "i dont know"
+    end
+  end
+end
+#refactor
+
+class Language
+  def speak name
+    language = Hash.new "i dont know"
+    language["english"] = "hello, english"
+    language["chinese"] = "hello, chinese"
+    language["Vietnam"] = "xin chao, Viet Nam"
+
+    puts language[name]
+  end
+end
+
+#4
+
+class Person
+  attr_reader :department
+
+  def initialize department
+    @department = department
+  end
+end
+
+class Department
+  attr_reader :manager
+
+  def initialize manager
+    @manager = manager
+  end
+end
+
+Khi muốn biết manager của person ta bắt buộc phải lấy qua department trước:
+manager = john.department.manager
+Code smell: Message Chains
+
+#Refactor: sử dụng Hide Delegate
+class Person
+  extend Forwardable
+  attr_reader :department
+
+  def initialize department
+    @department = department
+  end
+
+  def_delegator :@department, :manager
+end
+
+class Department
+  attr_reader :manager
+
+  def initialize manager
+    @manager = manager
+  end
+end
+
+
+#5
+class Dog
+  attr_reader :name
+
+  def initialize name
+    @name = name
+  end
+
+  def self.find_and_make_sound name
+    dog = Dogs.find{|dog| dog.name == name}
+    dog.make_sound if dog
+  end
+
+  def make_sound
+    puts "bark"
+  end
+end
+
+Dogs = [Dog.new("Bo"), Dog.new("Max")]
+Dog.find_and_make_sound("Bo") // => "bark"
+Dog.find_and_make_sound("Mac") // => nothing
+
+#Refactor: sử dụng Introduce Null Object
+
+class Dog
+  attr_reader :name
+
+  def initialize name
+    @name = name
+  end
+
+  def self.find_and_make_sound name
+    dog = Dogs.find{|dog| dog.name == name} || NilAnimal.new
+    dog.make_sound
+  end
+
+  def make_sound
+    puts "bark"
+  end
+end
+
+class NilAnimal
+  def make_sound
+  end
+end
+
+Dogs = [Dog.new("Bo"), Dog.new("Max")]
+Dog.find_and_make_sound("Bo") // => "bark"
+Dog.find_and_make_sound("Mac") // => nothing
+
+
+