Group 4

Homeworks/Anwer.md

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+Bài I:
+1. Single Respnosibility principle
+
+class AuthenticateAccount
+  def authenticate(email, password)
+    user = find_from_db(email)
+    if user.encrypted_password == encrypt(password)
+      # your code here
+    else
+      # your code here
+    end
+  end
+end
+# Class AuthenticateAccount đã thực hiện nhiều nhiệm vụ: Lấy dữ liệu từ db, validate password
+# Refactored
+class AuthenticateAccount
+  def authenticate(email, password)
+    if ValidatePasswords.new(email, password).validate?
+      # your code here
+    else
+      # your code here
+    end
+  end
+end
+
+class ValidatePasswords
+  def initialize(email, password)
+     @email = email
+     @password = password
+  end
+
+  def validate?
+    user = find_from_db(@email)
+    user.encrypted_password == encrypt(@password)
+  end
+end
+
+
+2. Open/Close principle
+
+class Dog
+  def speak
+    return "Go go"
+  end
+end
+
+class Cat
+  def speak
+    return "Meo Meo"
+  end
+end
+
+class ZooManager
+  def check_speak animal
+    if animal.class == "Dog"
+      return "Go go"
+    elsif animal.class == "Cat"
+      return "Meo Meo"
+    else
+      return ""
+    end
+  end
+end
+
+# Khó cho việc mở rộng thêm các class
+# Refactored
+module Animal
+  def speak
+    return ""
+  end
+end
+
+class Dog < Animal
+  def speak
+    return "Go go"
+  end
+end
+
+class Cat < Animal
+  def speak
+    return "Meo Meo"
+  end
+end
+
+class ZooManager
+  def check_speak animal
+    return animal.speak
+  end
+end
+
+3. Liskov substitution principle
+class Bird
+  def fly
+    return "Flying"
+  end
+end
+
+class Duck # Vit
+  def fly
+    return "Duck flying"
+  end
+end
+
+class Eagle # Diều hâu
+  def fly
+    return "Eagle flying"
+  end
+end
+
+class Penguins < Bird #Chim cánh cụt
+  def fly
+    begin
+      # you code here
+    rescue => e
+      # Exception
+    end
+  end
+end
+
+@bird = [Duck.new(), Eagle.new(), Penguins.new()]
+@bird.each{ bird | bird.fly}
+
+# Lỗi Exception bắn ra do chim cánh cụt không thể bay.
+
+4. Interface segregation principle
+
+module Car
+  def start_engine
+  end
+
+  def stop_engine
+  end
+
+  def change_engine
+  end
+end
+
+class Driver < Car
+  def driver
+    def start_engine
+      # your code here
+    end
+    def stop_engine
+      # your code here
+    end
+  end
+end
+
+class Mechanic
+  def mechanic
+    def change_engine
+      #your code here
+    end
+  end
+end
+
+# Class Driver không cần gánh thêm def change_engine, tương tự cho class Mechanic
+#Refactored
+module Car
+  def start_engine
+  end
+
+  def stop_engine
+  end
+end
+
+module CarInternals
+  def change_engine
+  end
+end
+
+class Driver < Car
+  def driver
+    def start_engine
+      # your code here
+    end
+    def stop_engine
+      # your code here
+    end
+  end
+end
+
+class Mechanic < CarInternals
+  def mechanic
+    def change_engine
+      #your code here
+    end
+  end
+end
+
+5. Dependency inversion principle
+
+class Student
+  def update_data
+    Database db = Database.new();
+    student = db.get_data();
+    # your code here
+    student = db.set_data();
+  end
+end
+
+class Databae
+  def get_data()
+    # your code here
+  end
+  def set_data()
+    # your code here
+  end
+end
+
+# Class Stusdent đang phụ thuộc vào class Database.
+# Nếu class Database thay đổi phương thức save thì class Student cũng phải thay đổi theo.
+# Giải pháp sử dụng Module IDatabase ở giữa, class Database và Student làm việc với nhau thông qua IDatabase.
+# Refactored
+module IDatabase
+  def get_data
+    # your code here
+  end
+  def set_data
+    # your code here
+  end
+end
+
+class Database < IDatabase
+  def get_data
+    # your code here
+  end
+  def set_data
+    # your code here
+  end
+end
+
+class Student < IDatabase
+  def update_data
+    Database db = IDatabase.new();
+    student = db.get_data();
+    # your code here
+    student = db.set_data();
+  end
+end
+
+Bài II: Framgia Crb
+
+Bài toán: Yêu cầu validate name khi signup. (Error syntag + duplicate in database)
+Hoàn toàn có thể validate name trong class User trưóc khi create User.
+Nhưng để đảm bảo Single Respnosibility:
+Coder đã viết riêng class Persion để validate name chứ không viết gộp trong class User.
+Cụ thể:
+[Persion Class](https://github.com/framgia/framgia_crb_v2/blob/develop/app/models/person.rb)