I have .net classes I am using unity as IOC for resolving our dependencies. It tries to load all the dependencies at the beginning. Is there a way (setting) in Unity which allows to load a dependency at runtime?
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4 Answers
There's even better solution - native support for Lazy<T> and IEnumerable<Lazy<T>> in the Unity 2.0. Check it out here.
1 Comment
Akira Yamamoto
Don't forget this line
unityContainer.AddNewExtension<LazySupportExtension>(); and the reference PM> Install-Package Unity.Extensions.Lazy Unity should be lazily constructing instances, I believe. Do you mean that it is loading the assemblies containing the other dependencies? If that's the case, you might want to take a look at MEF - it's designed specifically for modular applications.
Comments
I have blogged some code here to allow passing 'lazy' dependencies into your classes. It allows you to replace:
class MyClass(IDependency dependency)
with
class MyClass(ILazy<IDependency> lazyDependency)
This gives you the option of delaying the actual creation of the dependency until you need to use it. Call lazyDependency.Resolve() when you need it.
Here's the implementation of ILazy:
public interface ILazy<T>
{
T Resolve();
T Resolve(string namedInstance);
}
public class Lazy<T> : ILazy<T>
{
IUnityContainer container;
public Lazy(IUnityContainer container)
{
this.container = container;
}
public T Resolve()
{
return container.Resolve<T>();
}
public T Resolve(string namedInstance)
{
return container.Resolve<T>(namedInstance);
}
}
you will need to register it in your container to be able to use it:
container.RegisterType(typeof(ILazy<>),typeof(Lazy<>));
Comments
in .net core use "Lazy Resolution" : remove both constructor injection of both classes and instantiate other class only when need to use it by injecting the .net IServiceProvider namespace.
serviceProvider.GetRequiredService<Service2>().Hi();
Use constructor injection default and only use Lazy Resolution when you have to.
