Make Money comparable and and allow comparison accross currencies and also add tests for sorting.

Author: tobiasschuerg

gradlew

@@ -9,8 +9,8 @@ android {
 
     defaultConfig {
         minSdkVersion 14
-        versionCode 8
-        versionName "0.8.0"
+        versionCode 9
+        versionName "0.9.0"
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
 

money/build.gradle

@@ -10,7 +10,7 @@ import java.math.RoundingMode
  * Created by Tobias Schürg on 28.07.2017.
  */
 @Suppress("TooManyFunctions")
-data class Money(val amount: BigDecimal = BigDecimal.ZERO, val currency: Currency) {
+data class Money(val amount: BigDecimal = BigDecimal.ZERO, val currency: Currency) : Comparable<Money> {
 
     constructor(amount: Double, currency: Currency) : this(BigDecimal(amount), currency)
     constructor(amount: Long, currency: Currency) : this(BigDecimal(amount), currency)
@@ -21,9 +21,10 @@ data class Money(val amount: BigDecimal = BigDecimal.ZERO, val currency: Currenc
         return Money(sum, currency)
     }
 
-    operator fun compareTo(money: Money): Int {
-        requireSameCurrency(money)
-        return this.amount.compareTo(money.amount)
+    override operator fun compareTo(other: Money): Int {
+        val thisBaseCurrencyAmount = amount.divide(currency.rate, MathContext.DECIMAL32)
+        val otherBaseCurrencyAmount = other.amount.divide(other.currency.rate, MathContext.DECIMAL32)
+        return thisBaseCurrencyAmount.compareTo(otherBaseCurrencyAmount)
     }
 
     override fun toString(): String {

money/src/main/java/de/tobiasschuerg/money/Money.kt

@@ -0,0 +1,42 @@
+package de.tobiasschuerg.money
+
+import de.tobiasschuerg.money.Currencies.EURO
+import de.tobiasschuerg.money.Currencies.USDOLLAR
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotEquals
+import org.junit.Test
+
+class MoneySortingTest {
+
+    @Test
+    fun `test money sorting`() {
+
+        val money1 = Money(2, EURO)
+        val money2 = Money(17.11, EURO)
+        val money3 = Money(4.25, EURO)
+
+        val moneyListUnsorted = listOf(money1, money2, money3)
+
+        val sortedlist = moneyListUnsorted.sorted()
+        assertNotEquals(moneyListUnsorted, sortedlist)
+
+        val moneyListSortedManually = listOf(money1, money3, money2)
+        assertEquals(moneyListSortedManually, sortedlist)
+    }
+
+    @Test
+    fun `test money sorting with different currencies`() {
+
+        val money1 = Money(2, EURO)
+        val money2 = Money(2, USDOLLAR)
+        val money3 = Money(3, EURO)
+
+        val moneyListUnsorted = listOf(money1, money2, money3)
+
+        val sortedlist = moneyListUnsorted.sorted()
+        assertNotEquals(moneyListUnsorted, sortedlist)
+
+        val moneyListSortedManually = listOf(money2, money1, money3)
+        assertEquals(moneyListSortedManually, sortedlist)
+    }
+}

money/src/test/java/de/tobiasschuerg/money/MoneySortingTest.kt

@@ -28,6 +28,6 @@ dependencies {
 
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
     implementation 'androidx.appcompat:appcompat:1.2.0'
-    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    implementation 'androidx.constraintlayout:constraintlayout:2.0.0'
 
 }