不允许使用Angular2多个构造函数实现TS2392 [英] Angular2 multiple constructor implementations are not allowed TS2392

问题描述

如何在一个组件中使用多个构造函数?目前，我收到错误消息:

How can I get around using multiple constructors within a component? Currently I am getting the error:

不允许使用多个构造函数实现".

'Multiple constructor implementations are not allowed'.

questions: any[];
constructor( service: QuestionSignupStepOneService ) { 
    this.questions = service.getQuestions(); 
}
constructor( service: QuestionSignupStepOneAService ) { 
    this.questions = service.getQuestions(); 
}

无论如何，有没有简化我想要做的事情?该代码可以正确编译，但只能通过第一个服务运行，而忽略第二个服务.

Is there anyway to simplify what I am trying to do? The code compiles properly but will only run through the first service, ignoring the second.

推荐答案

使多个具有相同参数的构造函数没有意义，除非它们具有不同的类型，在Typescript中，您可以执行以下操作:

Making multiple constructors with the same parameters doesn't make sense unless they have different types, in Typescript you can do the following:

class Foo {
  questions: any[];
  constructor(service: QuestionSignupStepOneService, param2?: Param2Type) { 

    this.questions = service.getQuestions(); 
    if(param2){
        console.log(param2);
    }
  }
}

这等于两个构造函数，第一个是 new Foo(service)，第二个是 new Foo(service，param2).

This is equal to two constructors, the first one is new Foo(service) and the second one is new Foo(service, param2).

使用?声明该参数是可选的.

Use ? to state that the parameter is optional.

如果您希望两个构造函数具有相同的参数，但对于不同的类型，则可以使用以下方法:

If you want two constructors with the same parameter but for different types you can use this:

class Foo {
  questions: any[];
  constructor(service: QuestionSignupStepOneService | QuestionSignupStepOneAService) {

    if(service instanceof QuestionSignupStepOneService){
       this.questions = service.getQuestions(); 
    }
    else {
       this.questions = service.getDifferentQuestions(); 
    }
  }
}

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