From 8b03018712be112b43365ba9c59fd5d71558c877 Mon Sep 17 00:00:00 2001
From: Michal Bowzyk <m.bowzyk@getstrong.be>
Date: Sun, 3 Jun 2018 22:42:54 +0200
Subject: [PATCH] add tasks for objects and companion objects

---
 .../n13Objects.kt                             | 28 +++++++++++++++++++
 .../n14CompanionObject.kt                     | 24 ++++++++++++++++
 src/util/LinksToDocumentation.kt              | 12 ++++++++
 .../n13ObjectsKtTest.kt                       | 22 +++++++++++++++
 .../n14CompanionObjectKtTest.kt               | 22 +++++++++++++++
 5 files changed, 108 insertions(+)
 create mode 100644 src/i_introduction/_13_Object_And_Companion_Object/n13Objects.kt
 create mode 100644 src/i_introduction/_13_Object_And_Companion_Object/n14CompanionObject.kt
 create mode 100644 test/i_introduction/_13_Object_And_Companion_Object/n13ObjectsKtTest.kt
 create mode 100644 test/i_introduction/_13_Object_And_Companion_Object/n14CompanionObjectKtTest.kt

diff --git a/src/i_introduction/_13_Object_And_Companion_Object/n13Objects.kt b/src/i_introduction/_13_Object_And_Companion_Object/n13Objects.kt
new file mode 100644
index 000000000..408474ff6
--- /dev/null
+++ b/src/i_introduction/_13_Object_And_Companion_Object/n13Objects.kt
@@ -0,0 +1,28 @@
+package i_introduction._13_Object_And_Companion_Object
+
+import util.doc13
+
+fun todoTask13(): Nothing = util.TODO(
+        """
+        Task 13.
+        Kotlin supports creating thread-safe singletons, which can be useful in various situations.
+        You can declare them using object keyword.
+        When You want to use declared object, You don't need to add initializer.
+        `val example = ObjectExample`
+
+        Add `init { }` block, where You will increment `counterForCreation` property, and
+        implement getter for `counterForGetter`, which should return it and increment by one.
+        """,
+        documentation = doc13()
+)
+
+object ObjectExample {
+    var counterForCreation = 0
+        private set
+
+    var counterForGetter = 0
+        get() = todoTask13()
+        private set
+}
+
+
diff --git a/src/i_introduction/_13_Object_And_Companion_Object/n14CompanionObject.kt b/src/i_introduction/_13_Object_And_Companion_Object/n14CompanionObject.kt
new file mode 100644
index 000000000..99c2138c1
--- /dev/null
+++ b/src/i_introduction/_13_Object_And_Companion_Object/n14CompanionObject.kt
@@ -0,0 +1,24 @@
+package i_introduction._13_Object_And_Companion_Object
+
+import util.doc14
+
+fun todoTask14(): Nothing = util.TODO(
+        """
+        Task 14.
+        Similar behaviour have companion object.
+        It needs to be declared inside class and can implement interfaces or extends classes.
+        They can be use ie. for fabric method.
+        When integrating with Java code, sometimes We need to declare static functions, which We don't have in Kotlin.
+        Then We can use annotation `@JvmStatic`, but it can be use only inside objects on properties
+        or in companion objects on both functions ad properties.
+
+        Add companion object inside class below with property.
+        Make function `getCounter()` return it and increment by one.
+        """,
+        documentation = doc14()
+)
+
+class ExampleForCompanionObject {
+
+    fun getCounter(): Int = todoTask14()
+}
diff --git a/src/util/LinksToDocumentation.kt b/src/util/LinksToDocumentation.kt
index 4794940c1..9b015b67d 100644
--- a/src/util/LinksToDocumentation.kt
+++ b/src/util/LinksToDocumentation.kt
@@ -61,6 +61,18 @@ fun doc11() {}
  */
 fun doc12() {}
 
+/**
+ * @see <a href="https://kotlinlang.org/docs/reference/classes.html#constructors">Class constructors</a>,
+ * <a href="https://kotlinlang.org/docs/reference/object-declarations.html#object-declarations">Object declarations</a>
+ */
+fun doc13() {}
+
+/**
+ * @see <a href="https://kotlinlang.org/docs/reference/object-declarations.html#object-declarations">Object declarations</a>,
+ * <a href="https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html#static-fields">Static fields in java integrations</a>
+ */
+fun doc14() {}
+
 /**
  * @see <a href="https://kotlinlang.org/docs/reference/operator-overloading.html">Operator overloading</a>
  */
diff --git a/test/i_introduction/_13_Object_And_Companion_Object/n13ObjectsKtTest.kt b/test/i_introduction/_13_Object_And_Companion_Object/n13ObjectsKtTest.kt
new file mode 100644
index 000000000..fc2bb4b2d
--- /dev/null
+++ b/test/i_introduction/_13_Object_And_Companion_Object/n13ObjectsKtTest.kt
@@ -0,0 +1,22 @@
+package i_introduction._13_Object_And_Companion_Object
+
+import org.junit.Assert.assertThat
+import org.junit.Test
+import org.hamcrest.core.Is.`is` as isEqualTo
+
+class n13ObjectsKtTest {
+
+    @Test fun checkNumberOfInitialisations() {
+        val objectExample = ObjectExample
+
+        assertThat(objectExample.counterForCreation, isEqualTo(1))
+        assertThat(objectExample.counterForGetter, isEqualTo(0))
+        assertThat(objectExample.counterForGetter, isEqualTo(1))
+
+        val secondInit = ObjectExample
+        assertThat(secondInit.counterForCreation, isEqualTo(1))
+        assertThat(secondInit.counterForGetter, isEqualTo(2))
+
+        assertThat(objectExample.hashCode(), isEqualTo(secondInit.hashCode()))
+    }
+}
\ No newline at end of file
diff --git a/test/i_introduction/_13_Object_And_Companion_Object/n14CompanionObjectKtTest.kt b/test/i_introduction/_13_Object_And_Companion_Object/n14CompanionObjectKtTest.kt
new file mode 100644
index 000000000..b08e86555
--- /dev/null
+++ b/test/i_introduction/_13_Object_And_Companion_Object/n14CompanionObjectKtTest.kt
@@ -0,0 +1,22 @@
+package i_introduction._13_Object_And_Companion_Object
+
+import org.hamcrest.core.IsNot.not
+import org.hamcrest.core.Is.`is` as isEqualTo
+import org.junit.Assert.assertThat
+import org.junit.Test
+
+class n14CompanionObjectKtTest {
+
+    @Test
+    fun checkNumberOfInitialisations() {
+        val objectExample = ExampleForCompanionObject()
+
+        assertThat(objectExample.getCounter(), isEqualTo(0))
+        assertThat(objectExample.getCounter(), isEqualTo(1))
+
+        val secondInit = ExampleForCompanionObject()
+        assertThat(secondInit.getCounter(), isEqualTo(2))
+
+        assertThat(objectExample.hashCode(), not(isEqualTo(secondInit.hashCode())))
+    }
+}
\ No newline at end of file