Better Gradle Dependency Management

app/build.gradle

@@ -3,18 +3,14 @@ apply plugin: 'kotlin-android'
 apply plugin: 'kotlin-android-extensions'
 apply plugin: 'kotlin-kapt'
 
-ext.android_support_version = '26.1.0'
-ext.arch_version = '1.0.0'
-ext.retrofit_version = '2.3.0'
-
 android {
-    compileSdkVersion 26
-    buildToolsVersion '26.0.2'
+    compileSdkVersion Versions.compileSDK
+    buildToolsVersion Versions.buildTools
     defaultConfig {
         applicationId "com.akshay.newsapp"
-        minSdkVersion 15
-        versionCode 1
-        versionName "1.0"
+        minSdkVersion Versions.minSDK
+        versionCode Versions.versionCode
+        versionName Versions.versionName
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
         buildConfigField("String", "NEWS_API_KEY", NEWS_API_KEY)
         javaCompileOptions {
@@ -38,34 +34,34 @@ dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
 
     // Kotlin
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
+    implementation Deps.kotlin
 
     // Support Libraries
-    implementation "com.android.support:appcompat-v7:$android_support_version"
-    implementation "com.android.support:recyclerview-v7:$android_support_version"
-    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
+    implementation Deps.appCompat
+    implementation Deps.recyclerView
+    implementation Deps.constraintLayout
 
     // Retrofit
-    implementation "com.squareup.retrofit2:retrofit:$retrofit_version"
-    implementation "com.squareup.retrofit2:converter-gson:$retrofit_version"
-    implementation 'com.google.code.gson:gson:2.8.0'
+    implementation Deps.retrofit
+    implementation Deps.retrofitGsonConverter
+    implementation Deps.gson
 
     // Architecture Components
-    implementation "android.arch.lifecycle:extensions:$arch_version"
-    implementation "android.arch.persistence.room:runtime:$arch_version"
-
-    kapt "android.arch.lifecycle:compiler:$arch_version"
-    kapt "android.arch.persistence.room:compiler:$arch_version"
+    implementation Deps.lifecycle
+    kapt Deps.lifecycleCompiler
+    implementation Deps.coreTesting
+    // Room
+    implementation Deps.room
+    kapt Deps.roomCompiler
+    implementation Deps.roomTesting
 
     // Testing
-    testImplementation 'junit:junit:4.12'
-    debugImplementation 'com.amitshekhar.android:debug-db:1.0.1'
-    // Arch
-    testImplementation "android.arch.core:core-testing:$arch_version"
+    testImplementation Deps.junit
+    debugImplementation Deps.debugDb
     // Retrofit
-    testImplementation "com.squareup.okhttp3:mockwebserver:3.8.1"
+    testImplementation Deps.mockWebServer
     // UI
-    androidTestImplementation('com.android.support.test.espresso:espresso-core:2.2.2', {
+    androidTestImplementation(Deps.espresso, {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
 }

build.gradle

@@ -1,14 +1,13 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.1.51'
     repositories {
         google()
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+        classpath Deps.androidGradlePlugin
+        classpath Deps.kotlinGradlePlugin
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files

buildSrc/.gitignore

@@ -0,0 +1,5 @@
+*.iml
+.gradle
+/.idea
+/build
+gradle.properties

buildSrc/build.gradle.kts

@@ -0,0 +1,3 @@
+plugins {
+    `kotlin-dsl`
+}

buildSrc/src/main/java/Dependencies.kt

@@ -0,0 +1,72 @@
+/**
+ * A holder of all the versions.
+ */
+object Versions {
+
+    // Build Config
+    const val minSDK = 15
+    const val compileSDK = 26
+    const val targetSDK = 27
+    const val buildTools = "27.0.3"
+
+    // App version
+    const val versionCode = 2
+    const val versionName = "2.8.0"
+
+    // Plugins
+    const val androidGradlePlugin = "3.0.1"
+
+    // Dependencies
+    const val kotlin = "1.2.30"
+    const val support = "27.1.0"
+    const val constraintLayout = "1.0.2"
+    const val lifecycle = "1.1.0"
+    const val room = "1.0.0"
+    const val retrofit = "2.3.0"
+    const val gson = "2.8.2"
+    const val okHttp = "3.10.0"
+
+    // Testing
+    const val junit = "4.12"
+    const val espresso = "2.2.2"
+    const val debugDb = "1.0.1"
+}
+
+/**
+ * A holder of all the dependencies required by the app.
+ */
+object Deps {
+    // Kotlin
+    const val kotlin = "org.jetbrains.kotlin:kotlin-stdlib-jdk7:${Versions.kotlin}"
+    const val kotlinGradlePlugin = "org.jetbrains.kotlin:kotlin-gradle-plugin:${Versions.kotlin}"
+
+    // Support Library
+    const val appCompat = "com.android.support:appcompat-v7:${Versions.support}"
+    const val recyclerView = "com.android.support:recyclerview-v7:${Versions.support}"
+    const val constraintLayout = "com.android.support.constraint:constraint-layout:${Versions.constraintLayout}"
+
+    // Architecture Components
+    const val lifecycle = "android.arch.lifecycle:extensions:${Versions.lifecycle}"
+    const val lifecycleCompiler = "android.arch.lifecycle:compiler:${Versions.lifecycle}"
+    const val coreTesting = "android.arch.core:core-testing:${Versions.lifecycle}"
+    // Room
+    const val room = "android.arch.persistence.room:runtime:${Versions.room}"
+    const val roomCompiler = "android.arch.persistence.room:compiler:${Versions.room}"
+    const val roomTesting = "android.arch.persistence.room:testing:${Versions.room}"
+
+    // Retrofit
+    const val retrofit = "com.squareup.retrofit2:retrofit:${Versions.retrofit}"
+    const val retrofitGsonConverter = "com.squareup.retrofit2:converter-gson:${Versions.retrofit}"
+    const val gson = "com.google.code.gson:gson:${Versions.gson}"
+    const val mockWebServer = "com.squareup.okhttp3:mockwebserver:${Versions.okHttp}"
+
+    // Testing
+    const val junit = "junit:junit:{${Versions.junit}"
+    const val espresso = "com.android.support.test.espresso:espresso-core:${Versions.espresso}"
+    const val debugDb = "com.amitshekhar.android:debug-db:${Versions.debugDb}"
+
+
+    // Android Gradle Plugin
+    const val androidGradlePlugin = "com.android.tools.build:gradle:${Versions.androidGradlePlugin}"
+
+}