Constructor Injection

VContainer automatically collects and calls registered class constructors.

note

At this time, all the parameters of the constructor must be registered.
If the dependency cannot be resolved, throws exception when validating LifetimeScope or building Container.

Here is basic idiom with DI.

class ClassA
{
    readonly IServiceA serviceA;
    readonly IServiceB serviceB;
    readonly SomeUnityComponent component;

    public ClassA(
        IServiceA serviceA,
        IServiceB serviceB,
        SomeUnityComponent component)
    {
        this.serviceA = serviceA;
        this.serviceB = serviceB;
        this.component = component;
    }
}

caution

Constructors are often stripped in the IL2CPP environment. To prevent this problem, add the [Inject] Attribute explicitly.

    [Inject]
    public ClassA(
        IServiceA serviceA,
        IServiceB serviceB,
        SomeUnityComponent component)
    {
        // ...
    }

note

If class has multiple constructors, the one with [Inject] has priority.

Recommendation

Use Constructor Injection whenever possible. The constructor & readonly field idiom is:

The instantiated object has a compiler-level guarantee that the dependencies have been resolved.
No magic in the class code. Instantiate easily without DI container. (e.g. Unit testing)
If you look at the constructor, the dependency is clear.
- If too many constructor arguments, it can be considered overly responsible.

MonoBehaviour#

MonoBehaviour cannot use a constructor. Use method injection instead.