结合DI与构造函数参数? [英] Combining DI with constructor parameters?

问题描述

如何将构造函数注入与手动"构造函数参数结合起来?即.

How do I combine constructor injection with "manual" constructor parameters? ie.

public class SomeObject
{
    public SomeObject(IService service, float someValue)
    {
    }
}

我的DI容器应在哪里解析/注入IService，并应指定someValue.如何将两者混在一起?

Where IService should be resolved/injected by my DI container, and someValue should be specified. How do I mix the two?

推荐答案

应尽可能避免这种构造.因此，请问问自己:该参数是否真的需要作为构造函数参数?还是可以通过将参数传递给您在对象上执行的方法来将SomeObject替换为无状态的对象，从而使依赖该对象的每个人都可以重用它?

Such constructs should be avoided whenever possible. Therefore, ask yourself: is this parameter really required as constructor argument? Or can SomeObject be replaced by a stateless one which is reused by everyone that depends on it by passing the parameter to the method you execute on the object?

例如代替

public class SomeObject
{
    private float someValue
    public SomeObject(IService service, float someValue)
    {
        this.someValue = someValue
    }

    public float Do(float x)
    {
        return this.Service.Get(this.someValue) * x;
    }
}

使用

public class SomeObject
{
    public SomeObject(IService service)
    {
    }

    public float Do(float x, float someValue)
    {
        return this.Service.Get(someValue) * x;
    }
}

---

如果需要，请去工厂:

---

If it is required go for a factory:

public interface ISomeObjectFactory
{
    ISomeObject CreateSomeObject(float someValue);
}

public class SomeObjectFactory : ISomeObjectFactory
{
    private IKernel kernel;
    public SomeObjectFactory(IKernel kernel) 
    {
        this.Kernel = kernel;
    }

    public ISomeObject Create(float someValue)
    {
        return this.kernel.Get<ISomeObject>(WithConstructorArgument("someValue", someValue);
    }
}

预览: Ninject 2.4不再需要实现，但允许

Preview: Ninject 2.4 won't require the implementation anymore but allow

kernel.Bind<ISomeObjectFactory>().ToFactory();  // or maybe .AsFactory();

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