EventEmitter< undefined>之间有什么区别?和EventEmitter< void&gt ;? [英] What are the differences between EventEmitter<undefined> and EventEmitter<void>?

问题描述

有时候，我们可能会遇到应该省略泛型变量的情况. 像这样:

Some times we can have a case when generic variable should be omitted. Like this:

@Component( ... )
class MyComponent {

  @Output()
  public cancel = new EventEmitter<undefined>();

  private myFoo() {
    this.cancel.emit(); // no need to pass any value
  }
}

因此，问题:哪种是定义EventEmitter类型的更好方法:
EventEmitter<undefined>或EventEmitter<void>.

So, the question: Which is better way to define the EventEmitter type:
EventEmitter<undefined> or EventEmitter<void>.

• void更好，因为在.emit()调用中没有参数.
• undefined更好.emit()是相同的.emit(undefined)

• void is better because there is no an argument in .emit() call.
• undefined is better .emit() is the same .emit(undefined)

您对此有何看法?

推荐答案

根据TypeScript文档，void类型同时接受undefined和null-因此，以下代码将有效:

According to the TypeScript docs, the void type accepts both undefined and null - therefore, the following code would be valid:

@Component( ... )
class MyComponent {

  @Output()
  public cancel = new EventEmitter<void>();

  private myFoo() {
    this.cancel.emit();
    this.cancel.emit(undefined);
    this.cancel.emit(null);
  }
}

使用EventEmitter<undefined>时，您只能传递undefined或不传递任何参数，这在您的情况下可能更正确-也就是说，我看不到仅由于您传递了到您都不希望有任何值的发射器，因此我很想选择void，因为它是较短的选项.

Whereas with EventEmitter<undefined>, you would only be able to pass undefined or no argument, which is probably more correct in your case - that said, I can't see any major issues occurring just because you passed null to an emitter that you're not expecting a value from anyway, so I'd be tempted to choose void since it's the shorter option.

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