LazyDagger

KSP Compiler Plugin for Dagger Lazy Delegates

Generated by Stable Diffusion for "Sleeping face on a dagger"

Dagger supports Lazy Provider wrapper to delay expensive object creation. When used wisely, it can greatly improve the startup time of your app. However, this invites a lot of boilerplate similar to backing properties in Kotlin. For instance,

// non-lazy implementation
class CommentViewModel(
    val analyticsManager: AnalyticsManager,
    val authRepository: AuthRepository,
    val deleteUseCase: DeleteUseCase
) {
    ...
}

// lazy setup
interface CommentViewModelLazyDelegate {
    val analyticsManager: AnalyticsManager
    val authRepository: AuthRepository
    val deleteUseCase: DeleteUseCase
}

class CommentViewModelLazyDelegateImpl @Inject constructor(
    val analyticsManagerLazy: Lazy<AnalyticsManager>,
    val authRepositoryLazy: Lazy<AuthRepository>,
    val deleteUseCaseLazy: Lazy<DeleteUseCase>
) : CommentViewModelLazyDelegate {
    val analyticsManager: AnalyticsManager by lazy { analyticsManagerLazy.get() }
    val authRepository: AuthRepository by lazy { authRepositoryLazy.get() }
    val deleteUseCase: DeleteUseCase by lazy { deleteUseCaseLazy.get() }
}

@HiltViewModel
class CommentViewModel @Inject constructor(
    lazyDelegate: CommentViewModelLazyDelegate
) : CommentViewModelLazyDelegate by lazyDelegate {
    ...
}

While we could have kept the backing properties in the original ViewModel itself, we can't get away with the amount of boilerplate involved in this process (2 x No. of Lazy Injections). LazyDagger helps you get away from this situation by generating this code for you.

Usage

Simply add @LazyDagger annotation to your interface and the implementation will be generated alongside the Hilt binding modules for specified component(s) or SingletonComponent::class if not specified. Check the sample/ project to learn more

package com.lazydagger.sample

@LazyDagger(ActivityRetainedComponent::class)
interface CommentViewModelLazyDelegate {
    val analyticsManager: AnalyticsManager
    val authRepository: AuthRepository
    val deleteUseCase: DeleteUseCase
}

// will auto-generate
@OriginatingElement(topLevelClass = CommentViewModelLazyDelegate::class)
public class CommentViewModelLazyDelegateImpl @Inject constructor(
  private val analyticsManagerLazy: Lazy<AnalyticsManager>,
  private val authRepositoryLazy: Lazy<AuthRepository>,
  private val deleteUseCaseLazy: Lazy<DeleteUseCase>,
) : CommentViewModelLazyDelegate {
  public override val analyticsManager: AnalyticsManager by lazy { analyticsManagerLazy.get() }

  public override val authRepositoryLazy: AuthRepository by lazy { authRepositoryLazy.get() }
  
  public override val deleteUseCase: DeleteUseCase by lazy { deleteUseCaseLazy.get() }
}

@Module
@InstallIn(dagger.hilt.android.components.ActivityRetainedComponent::class)
internal abstract class ActivityRetainedComponent_LazyDaggerModule {
  @Binds
  internal abstract
      fun bind_com_lazydagger_sample_CommentViewModelLazyDelegate(`impl`: CommentViewModelLazyDelegateImpl):
      CommentViewModelLazyDelegate
}

Install

Add KSP plugin, gradle dependency and include generated ksp directory to your sourceSets

plugins {
    id("com.google.devtools.ksp") version "<version>"
}

dependencies {
    implementation("com.kshitijpatil.lazydagger:lazydagger-core:$lazydaggerVersion")
    ksp("com.kshitijpatil.lazydagger:lazydagger-codegen:$lazydaggerVersion")
}

sourceSets.main {
    java.srcDirs("build/generated/ksp/main/kotlin")
}

License

Copyright 2022 Kshitij Patil

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.