Injector

Additional

Language
Kotlin
Version
1.0.0 (Oct 15, 2019)
Created
Oct 15, 2019
Updated
Oct 16, 2019
Owner
Eugene (eugeneek)
Contributor
Eugene (eugeneek)
1
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Injector

Simple two-classes DI container with scopes. Written in Kotlin but Java-friendly.

How to use

Inherit Scope class to create scoped container for your instances. Create instances and bind() them to this scope. Open created scope and request instances whenever you need with object Injector. Close scope in right place to avoid memory leaks

Create instances

For example, let's create scope, that will contains object ResourceManager. It responsible for providing text resources through Android SDK's Resources class.

class MainScope(  
    private val context: Context  
): Scope() {  
  
    override fun init() {  
        // initialization
        val resourceManager = ResourceManager(context.resources)
        
        // binding
        bind(resourceManager)
    }  
}

Open/close scope

For ResourceManager it is important to has actual Resources object for accessing right resources (depends on Locale, screen orientation, etc.), so we can open and close scope in related lifecycle callback methods of our MainActivity:

...
override fun attachBaseContext(newBase: Context?) {  
    super.attachBaseContext(newBase)  
 
 val mainScope = MainScope(this)  
    Injector.openScope(mainScope, AppScope::class)  
}
...
override fun onDestroy() {  
    super.onDestroy()  
 
 Injector.closeScope(MainScope::class)
}

Here AppScope::class is a reference to a parent scope. All scopes should have a parent scope, excluding one root scope. Only one root scope can be opened without mentioning a parens scope: Injector.openScope(appScope)

Request instances

Finally you can request bound instances whenever you need it:

// directly
val resourceManager: ResourceManager = get()
// or lazy
val resourceManager: ResourceManager by inject()

Even in other scopes:

class Mapper(resourceManager: ResourceManager)

class ChildScope: Scope() {  
      
    override fun init() {  
        // initialization
        val mapper = Mapper(
            resourceManager = get()
        )
        
        // binding
        bind(mapper)
    }  
}

Add to project

Distributed by JitPack Step 1. Add the JitPack repository to your build file Add it in your root build.gradle at the end of repositories:

allprojects {
    repositories {
        ...
        maven { url 'https://jitpack.io' }
    }
} 

Step 2. Add the dependency

dependencies {
    implementation 'com.github.eugeneek:injector:1.0.1'
}