/PlainDI

Primary LanguageC#MIT LicenseMIT

PlainDI

Plain DI library without the need for containers.

Example

using PlainDI.Attribute;

[Injectable(typeof(Service))] 
public interface IService  {
    //...
}

public class Service : IService {
    //...
}
using PlainDI;
using PlainDI.Attribute;

public class Client {
    [Inject] IService service;
    //...
}

static void Main(string[] args) {
    Client client = Injector.Get<Client>();
    //...
}

Injector Class

Namespace: PlainDI

Exposes all the functionality of the DI library.

public sealed class Injector

Inheritance Object → Injector

Static Methods

Signature Description
T Get<T>() Instantiate and return object of type T with injected services.
object Get(Type) Instantiate and return object with injected services.
void InjectExisting(object) Inject services into an existing object. Only injects to its fields and properties.

Injector.Get<T>()

Create and return an object of type T with injected services.

Type Parameters

T

The type of the object to create.

Returns

T

The instantiated object.

Exceptions

AttributeException

Thrown if [Injectable] does not decorate either an interface or an abstract class.

AttributeException

Thrown if there are multiple constructors with [Default] attributes.

NoImplementationException

Thrown if [Injectable] targetInstance does not implement T.

CircularDependencyException

Thrown if a dependency is found referencing an earlier service.

MissingMethodException

Thrown if DI library cannot find a suitable constructor for T.

Injector.Get(Type type)

Create and return an object of type with injected services.

Parameters

Type type

The type of the object to create.

Returns

object

The instantiated object.

Exceptions

AttributeException

Thrown if [Injectable] does not decorate either an interface or an abstract class.

AttributeException

Thrown if there are multiple constructors with [Default] attributes.

NoImplementationException

Thrown if [Injectable] targetInstance does not implement type.

CircularDependencyException

Thrown if a dependency is found referencing an earlier service.

MissingMethodException

Thrown if DI library cannot find a suitable constructor for type.

Injector.InjectExisting(object obj)

Inject services into an existing object. Only injects to its fields and properties.

Parameters

object obj

The object to inject fields and properties.

Exceptions

AttributeException

Thrown if [Injectable] does not decorate either an interface or an abstract class.

AttributeException

Thrown if there are multiple constructors with [Default] attributes.

NoImplementationException

Thrown if [Injectable] targetInstance does not implement type.

CircularDependencyException

Thrown if a dependency is found referencing an earlier service.

MissingMethodException

Thrown if DI library cannot find a suitable constructor for type.

Injector.Invoke(Delegate function)

Calls a function and injects objects into its parameters.

Parameters

Delegate function

The function to call.

Returns

object?

The object returned from the function else null.

Exceptions

AttributeException

Thrown if [Injectable] does not decorate either an interface or an abstract class.

AttributeException

Thrown if there are multiple constructors with [Default] attributes.

NoImplementationException

Thrown if [Injectable] targetInstance does not implement type.

CircularDependencyException

Thrown if a dependency is found referencing an earlier service.

MissingMethodException

Thrown if DI library cannot find a suitable constructor for type.

Example

using PlainDI.Attribute;

[Injectable(typeof(Service))] 
public interface IService  {
    //...
}

public class Service : IService {
    //...
}
using PlainDI;
using PlainDI.Attribute;

public class Client {
    public void Foo(IService service) {
        //...
    }
}

static void Main(string[] args) {
    //...
    Injector.Invoke((Action<IService>)client.Foo);
}

[Injectable] attribute

Namespace: PlainDI.Attribute

[AttributeUsage(AttributeTargets.Interface | AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
public class InjectableAttribute : Attribute

Inheritance Object → Attribute → InjectableAttribute

Attributes AttributeUsageAttribute

Constructor

InjectableAttribute(Type targetInstance, Lifetime lifetime = Lifetime.Transient)

Parameters

Parameter Description
targetInstance Chosen implementation of the interface to use that will be injected to clients.
lifetime Specifies when a service is created for each client. Default transient.

Remarks

  • [Injectable] can only be applied to an interface or abstract classes.
  • Requiring to specify targetInstance solves the ambiguity of which implementation to use in the case of multiple implementations.
  • There are three types of lifetimes:
Lifetimes Description
Scoped Same instance for each client but different between clients.
Transient Different instances for every request.
Singleton Single instance shared across all clients.

[Inject] attribute

Namespace: PlainDI.Attribute

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false)]
public class InjectAttribute : Attribute

Inheritance Object → Attribute → InjectAttribute

Attributes AttributeUsageAttribute

Constructor

InjectAttribute()

Remarks

  • [Inject] can only be applied to fields or properties.
  • Decorated fields and properties will be injected regardless of access modifiers
  • Static fields and properties can also be injected

[Default] attribute

Namespace: PlainDI.Attribute

[AttributeUsage(AttributeTargets.Constructor)]
public class DefaultAttribute : Attribute

Inheritance Object → Attribute → DefaultAttribute

Attributes AttributeUsageAttribute

Constructor

DefaultAttribute()

Remarks

  • The [Default] attribute is used to mark which constructor to use when assembling an object.
  • Decorating a constructor is necessary if there are multiple declared constructors.
  • If there are no declared constructors or multiple undecorated constructors, the DI library will use the empty parameter constructor.