带可选参数的DI构造函数 [英] DI constructor with optional parameters

问题描述

我的构造函数具有可选参数，它们似乎与执行DI的主要方式搞混了.

My constructor has optional parameters and they seem to mess with the predominant way of doing DI.

constructor(public name:string, public age?:number, private _service:Service);

可以理解，

Typescript不喜欢我在一个可选参数后面放置一个非可选参数，此外，当未设置可选参数时，不会注入服务.我该如何解决?我不能将其放置在构造函数中的其他位置，因为会期望手动设置服务.

Typescript understandably doesn't like that I put a non optional parameter behind an optional one, furthermore the service doesn't get injected when the optional parameter isn't set. How do I solve that? I can't put it somewhere else in the constructor since I would be expected setting the service manually.

有像场注入之类的东西吗?

Is there something like field injection?

@Inject() private _service:Service;

constructor(public name:string, public age?:number);

是否应将可选参数替换为默认值?还有其他建议吗?

Should I replace the optional parameters with default values? Any other suggestions?

如下所述，我试图将服务注入到不是由Angular的DI创建的对象中.这行不通.由于无法使用DI创建此类(模型)，因此我现在从实例化此对象的类中手动传递服务.

As discussed below, I tried to inject a service into an object that isn't created by Angular's DI. This doesn't work. Since I can't create this class (model) using DI I now pass the service manually from the class that instantiates this objects.

推荐答案

只需添加 @Optional() 在构造函数参数之前的装饰器，只有在已注册提供者的情况下，才应插入.

Just add the @Optional() decorator before the constructor parameter that should only be injected if there was a provider registered.

constructor(public name:string, @Optional() public age:number)

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