igorwojda / IoCContainer

IoCContainer in pure Kotlin

What is it

Basic IoC container written in pure Kotlin.

How to run project

Checkout project and open it in InteliJ IDEA. Open Main.kt file to see a sample application.

To run tests open Gradle View and run Tasks - Verification - test task.

Features

• Constructor injection
• Nested dependency resolution
• Dependency verification
• Circular dependency detection
• Create instance of type with parameterless constructor (without need to register)
• Supports @Inject annotation
• Supports Kotlin Objects
• Supports @Singleton annotation
• Error handling (around access modifiers, abstract classes and interfaces, etc.)

Examples

Getting an instance of the Container:

val container = DependencyContainer.getInstance()

Register instance:

container.registerBinding(Foo::class, FooImpl::class)

Resolve class with parameterless constructor:

class FooImpl: Foo

val container = DependencyContainer.getInstance()

// No registration in contaier is required for class with parameterless constructor
val instance = container.resolveBinding<FooImpl>()
println(instance) // FooImpl

Resolve binding for the interface:

interface Foo
class FooImpl: Foo

val container = DependencyContainer.getInstance()
// Given interface Foo return FooImpl instance
container.registerBinding(Foo::class, FooImpl::class)

val instance = container.resolveBinding<Foo>()
println(instance) // FooImpl

Retrieve class with nested dependency:

interface Foo
class FooImpl: Foo
class Bar(val foo:FooImpl)

val container = DependencyContainer.getInstance()
container.registerBinding(Foo::class, FooImpl::class)

val instance = container.resolveBinding<Bar>()
println(instance) // Bar

Inject singleton:

@Singleton
class Foo

val instance1 = container.resolveBinding<Foo>()
val instance2 = container.resolveBinding<Foo>()

insatnce1 === instance2

More examples can be found in DependencyContainerTest class.

Dependency verification

It is possible to verify all bindings in the container. This option is useful to check if all bindings can be resolved correctly.

val container = DependencyContainer.getInstance()
...
container.verifyBindings()