Group 6

Homeworks/Answer.md

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+class User < ActiveRecord::Base
+  attr_accessor :name, :age, :gender, :type
+
+  has_many :tests
+
+  belongs_to :school
+  belongs_to :class
+
+  def initialize(user)
+    @user = user
+  end
+
+  def get_name
+    user.name
+  end
+
+  def get_age
+    user.age
+  end
+
+  def open_class
+    Class.create(user_id: self.id) if user.type == 'teacher'
+  end
+
+  def add_user_to_school user, school
+    user.update_attribute school_id: school.id
+    if user.age <= 18
+      user.update_attributes type: 'student'
+    elsif user.age > 18 && user.age < 25
+      user.update_attributes type: 'teaching assistant'
+    else
+      user.update_attributes type: 'teacher'
+    end
+  end
+end
+
+#  This violate the single responsibility and open as the class User has
+#  more than one responsibility: the class is changed base on 4 reasons:
+#  - defining relation with another class
+#  - fetch user information
+#  - Create class if user is a teacher, and have him/herself as class teacher
+#  - Add user to school based on their types
+# Also, the open closed principle is violated because of the function add_user_to_school.
+# Assuming we move it to another class called "Assign user role", if there are more user types come up such as
+# secretary, class monitor, there would be more "elsif" and that would make the function hard to maintain
+
+# Solution: Split into smaller class :
+
+class User
+  def initialize(user); end
+  belongs_to :school
+  belongs_to :class
+end
+
+class GetUserProfile
+  def get_name; end
+  def get_age; end
+end
+
+class ManageClass
+  def create_class user
+    Class.create(user_id: user.id)
+  end
+end
+
+# Open closed:
+
+class AssignBaseRole
+  def add_user_to_school user, school
+    user.update_attributes school_id: school.id
+  end
+end
+
+
+class AssignStudent
+end
+
+class AssignTeacher
+end
+
+
+##homework2
+## https://github.com/mikeknep/SOLID/blob/master/interface_segregation/good/src/
+public class Penguin implements SwimmingCreature, FeatheredCreature {
+  String currentLocation;
+  int numberOfFeathers;
+
+  public Penguin(int initialFeatherCount) {
+      this.numberOfFeathers = initialFeatherCount;
+  }
+
+  public void swim() {
+      this.currentLocation = "in the water";
+  }
+
+  public void molt() {
+      this.numberOfFeathers -= 4;
+  }
+}
+## Ơ đây, người ta thay vì dùng một interface lớn thì họ đã chia thành nhiều interface nhỏ với mục đích cụ thể(có thể bơi, có thể bay,lông vũ.. cho các loài chim)
+
+##https://github.com/mikeknep/SOLID/blob/master/dependency_inversion/good/src
+
+#EmailClient.java
+public class EmailClient implements Notifier {
+    public void alertWeatherConditions(String weatherConditions) {
+        if (weatherConditions == "sunny");
+            System.out.print("It is sunny");
+    }
+}
+# MobileDevice.java
+public class MobileDevice implements Notifier {
+    public void alertWeatherConditions(String weatherConditions) {
+        if (weatherConditions == "rainy")
+            System.out.print("It is rainy");
+    }
+}
+# WeatherTracker.java
+public class WeatherTracker {
+    String currentConditions;
+
+    public void setCurrentConditions(String weatherDescription) {
+        this.currentConditions = weatherDescription;
+    }
+
+    public void notify(Notifier notifier) {
+        notifier.alertWeatherConditions(currentConditions);
+    }
+}
+
+## Ơ đây, public void notify(Notifier notifier) hàm lấy gía trị đầu vào là một notifier mà không cần quan tâm đấy là notifier của loại nào, không phụ thuộc vào module cấp thấp hơn, mà phụ thuộc vào abstraction.