adding code examples from the book

Author: mdodsworth

code-examples/AdvOOP/objects/PersonUser.java

@@ -0,0 +1,12 @@
+// code-examples/AdvOOP/objects/PersonUser.java
+
+package objects;
+
+public class PersonUser {
+  public static void main(String[] args) {
+    // The following line won't compile.
+    // Person buck = Person.apply("Buck Trends", 100);
+    Person buck = PersonFactory.make("Buck Trends", 100);
+    System.out.println(buck);
+  }
+}

code-examples/AdvOOP/objects/PersonUserWontCompile.java

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+// code-examples/AdvOOP/objects/PersonUserWontCompile.java
+// WON'T COMPILE
+
+package objects;
+
+public class PersonUserWontCompile {
+  public static void main(String[] args) {
+    Person buck = Person.apply("Buck Trends", 100);  // ERROR
+    System.out.println(buck);
+  }
+}

code-examples/AdvOOP/objects/button-unapply-spec.scala

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+// code-examples/AdvOOP/objects/button-unapply-spec.scala
+
+package objects
+import org.specs._
+
+object ButtonUnapplySpec extends Specification {
+  "Button.unapply" should {
+    "match a Button object" in {
+      val b = new Button("click me")
+      b match {
+        case Button(label) => label mustEqual "click me"
+        case _ => fail()
+      }
+    }
+    "match a RadioButton object" in {
+      val b = new RadioButton(false, "click me")
+      b match {
+        case Button(label) => label mustEqual "click me"
+        case _ => fail()
+      }
+    }
+    "not match a non-Button object" in {
+      val tf = new TextField("hello world!")
+      tf match {
+        case Button(label) => fail()
+        case x => x must notBeNull // hack to make Specs not ignore this test.
+      }
+    }
+    "extract the Button's label" in {
+      val b = new Button("click me")
+      b match {
+        case Button(label) => label mustEqual "click me"
+        case _ => fail()
+      }
+    }
+    "extract the RadioButton's label" in {
+      val rb = new RadioButton(false, "click me, too")
+      rb match {
+        case Button(label) => label mustEqual "click me, too"
+        case _ => fail()
+      }
+    }
+  }
+}

code-examples/AdvOOP/objects/button.scala

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+// code-examples/AdvOOP/objects/button.scala
+
+package objects
+import ui3.Clickable
+
+class Button(val label: String) extends Widget with Clickable {
+  
+  def click() = {
+    // Logic to give the appearance of clicking a button...
+  }
+  
+  def draw() = {
+    // Logic to draw the button on the display, web page, etc.
+  }
+  
+  override def toString() = "(button: label="+label+", "+super.toString()+")"
+}
+
+object Button {
+  def unapply(button: Button) = Some(button.label)
+}

code-examples/AdvOOP/objects/list-apply-example-script.scala

@@ -0,0 +1,8 @@
+// code-examples/AdvOOP/objects/list-apply-example-script.scala
+
+val list1 = List()
+val list2 = List(1, 2.2, "three", 'four)
+val list3 = List("1", "2.2", "three", "four")
+println("1: "+list1)
+println("2: "+list2)
+println("3: "+list3)

code-examples/AdvOOP/objects/list-unapply-example-script.scala

@@ -0,0 +1,7 @@
+// code-examples/AdvOOP/objects/list-unapply-example-script.scala
+
+val list = List(1, 2.2, "three", 'four)
+list match {
+  case List(x, y, _*) => println("x = "+x+", y = "+y)
+  case _ => throw new Exception("No match! "+list)
+}

code-examples/AdvOOP/objects/person-factory.scala

@@ -0,0 +1,7 @@
+// code-examples/AdvOOP/objects/person-factory.scala
+
+package objects
+
+object PersonFactory {
+  def make(name: String, age: Int) = new Person(name, age)
+}

code-examples/AdvOOP/objects/person.scala

@@ -0,0 +1,23 @@
+// code-examples/AdvOOP/objects/person.scala
+
+package objects
+
+class Person(val name: String, val age: Int) {
+  override def toString = "name: " + name + ", age: " + age
+}
+
+object Person {
+  def apply(name: String, age: Int) = new Person(name, age)
+  def unapply(person: Person) = Some((person.name, person.age))
+  
+  def main(args: Array[String]) = {
+    // Test the constructor...
+    val person = new Person("Buck Trends", 18)
+    assert(person.name == "Buck Trends")
+    assert(person.age  == 21)
+  }
+}
+
+object PersonTest {
+  def main(args: Array[String]) = Person.main(args)
+}

code-examples/AdvOOP/objects/radio-button-unapply-spec.scala

@@ -0,0 +1,40 @@
+// code-examples/AdvOOP/objects/radio-button-unapply-spec.scala
+
+package objects
+import org.specs._
+
+object RadioButtonUnapplySpec extends Specification {
+  "RadioButton.unapply" should {
+    "should match a RadioButton object" in {
+      val b = new RadioButton(true, "click me")
+      b match {
+        case RadioButton(on, label) => label mustEqual "click me"
+        case _ => fail()
+      }
+    }
+    "not match a Button (parent class) object" in {
+      val b = new Button("click me")
+      b match {
+        case RadioButton(on, label) => fail()
+        case x => x must notBeNull
+      }
+    }
+    "not match a non-RadioButton object" in {
+      val tf = new TextField("hello world!")
+      tf match {
+        case RadioButton(on, label) => fail()
+        case x => x must notBeNull
+      }
+    }
+    "extract the RadioButton's on/off state and label" in {
+      val b = new RadioButton(true, "click me")
+      b match {
+        case RadioButton(on, label) => {
+          label mustEqual "click me"
+          on    mustEqual true
+        }
+        case _ => fail()
+      }
+    }
+  }
+}

code-examples/AdvOOP/objects/radio-button.scala

@@ -0,0 +1,14 @@
+// code-examples/AdvOOP/objects/radio-button.scala
+
+package objects
+
+/**
+ * Button with two states, on or off, like an old-style, 
+ * channel-selection botton on a radio.
+ */
+class RadioButton(val on: Boolean, label: String) extends Button(label)
+
+object RadioButton {
+  def unapply(button: RadioButton) = Some((button.on, button.label))
+                 // equivalent to: = Some(Pair(button.on, button.label))
+}

code-examples/AdvOOP/objects/text-field-unapply-spec.scala

@@ -0,0 +1,29 @@
+// code-examples/AdvOOP/objects/text-field-unapply-spec.scala
+package objects
+import org.specs._
+
+object TextFieldUnapplySpec extends Specification {
+    "TextField.unapply" should {
+        "should match a TextField object" in {
+            val tf = new TextField("hello world!")
+            tf match {
+                case TextField(text) => text mustEqual "hello world!"
+                case _ => fail()
+            }
+        }
+        "not match a non-TextField object" in {
+            val b = new Button("click me")
+            b match {
+                case TextField(text) => fail()
+                case x => x must notBeNull
+            }
+        }
+        "extract the text field's text" in {
+            val tf = new TextField("hello world!")
+            tf match {
+                case TextField(text) => text mustEqual "hello world!"
+                case _ => fail()
+            }
+        }
+    }
+}

code-examples/AdvOOP/objects/text-field.scala

@@ -0,0 +1,20 @@
+// code-examples/AdvOOP/objects/text-field.scala
+package objects
+import ui3.Clickable
+
+class TextField(var text: String) extends Widget with Clickable {
+    
+    def click() = {
+        // ... logic to select the appropriate point in the text.
+    }
+    
+    def draw() = {
+        // ... logic to draw the text field on the display, web page, etc.
+    }
+    
+    override def toString() = "(textfield: text="+text+", "+super.toString()+")"
+}
+
+object TextField {
+    def unapply(textField: TextField) = Some(textField.text)
+}

code-examples/AdvOOP/objects/widget-apply-spec.scala

@@ -0,0 +1,30 @@
+// code-examples/AdvOOP/objects/widget-apply-spec.scala
+
+package objects
+import org.specs._
+
+object WidgetApplySpec extends Specification {
+  "Widget.apply with a valid widget specification string" should {
+    "return a widget instance with the correct fields set" in {
+      Widget("(button: label=click me, (Widget))") match {
+        case Some(w) => w match {
+          case b:Button => b.label mustEqual "click me"
+          case x => fail(x.toString())
+        }
+        case None => fail("None returned.")
+      }
+      Widget("(textfield: text=This is text, (Widget))") match {
+        case Some(w) => w match {
+          case tf:TextField => tf.text mustEqual "This is text"
+          case x => fail(x.toString())
+        }
+        case None => fail("None returned.")
+      }
+    }
+  }
+  "Widget.apply with an invalid specification string" should {
+    "return None" in {
+      Widget("(button: , (Widget)") mustEqual None
+    }
+  }
+}

code-examples/AdvOOP/objects/widget.scala

@@ -0,0 +1,20 @@
+// code-examples/AdvOOP/objects/widget.scala
+
+package objects
+
+abstract class Widget {
+  def draw(): Unit
+  override def toString() = "(widget)"
+}
+
+object Widget {
+  val ButtonExtractorRE = """\(button: label=([^,]+),\s+\(Widget\)\)""".r
+  val TextFieldExtractorRE = """\(textfield: text=([^,]+),\s+\(Widget\)\)""".r
+
+  def apply(specification: String): Option[Widget] = specification match {
+    case ButtonExtractorRE(label)   => new Some(new Button(label))
+    case TextFieldExtractorRE(text) => new Some(new TextField(text))
+    case _ => None
+  }
+}
+

code-examples/AdvOOP/observer/button-observer2-spec.scala

@@ -0,0 +1,38 @@
+// code-examples/AdvOOP/observer/button-observer2-spec.scala
+
+package ui
+import org.specs._
+import observer._
+
+object ButtonObserver2Spec extends Specification {
+  "An Observer watching a SubjectForReceiveUpdateObservers button" should {
+    "observe button clicks" in {
+      val observableButton = 
+        new Button(name) with SubjectForReceiveUpdateObservers {
+        override def click() = { 
+          super.click()
+          notifyObservers
+        }
+      }
+      val buttonObserver = new ButtonCountObserver
+      observableButton.addObserver(buttonObserver)
+      for (i <- 1 to 3) observableButton.click()
+      buttonObserver.count mustEqual 3
+    }
+  }
+  "An Observer watching a SubjectForFunctionalObservers button" should {
+    "observe button clicks" in {
+      val observableButton = 
+        new Button(name) with SubjectForFunctionalObservers {
+        override def click() = { 
+          super.click()
+          notifyObservers
+        }
+      }
+      var count = 0
+      observableButton.addObserver((button) => count += 1)
+      for (i <- 1 to 3) observableButton.click()
+      count mustEqual 3
+    }
+  }
+}

code-examples/AdvOOP/observer/observer2.scala

@@ -0,0 +1,25 @@
+// code-examples/AdvOOP/observer/observer2.scala
+
+package observer
+
+trait AbstractSubject {
+  type Observer
+
+  private var observers = List[Observer]()
+  def addObserver(observer:Observer) = observers ::= observer
+  def notifyObservers = observers foreach (notify(_))
+
+  def notify(observer: Observer): Unit
+}
+
+trait SubjectForReceiveUpdateObservers extends AbstractSubject {
+  type Observer = { def receiveUpdate(subject: Any) }
+
+  def notify(observer: Observer): Unit = observer.receiveUpdate(this)
+}
+
+trait SubjectForFunctionalObservers extends AbstractSubject {
+  type Observer = (AbstractSubject) => Unit
+
+  def notify(observer: Observer): Unit = observer(this)
+}

code-examples/AdvOOP/overrides/abs-method-field-class-script.scala

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+// code-examples/AdvOOP/overrides/abs-method-field-class-script.scala
+
+abstract class AbstractParent {
+  def name: String
+}
+
+class ConcreteChild extends AbstractParent {
+  val name = "Child"
+}
+
+println(new ConcreteChild().name)   // => "Child"

code-examples/AdvOOP/overrides/abs-method-field-trait-script.scala

@@ -0,0 +1,11 @@
+// code-examples/AdvOOP/overrides/abs-method-field-trait-script.scala
+
+trait AbstractNameTrait {
+  def name: String
+}
+
+class ConcreteNameClass extends AbstractNameTrait {
+  val name = "ConcreteNameClass"
+}
+
+println(new ConcreteNameClass().name)   // => "ConcreteNameClass"