如何在 Dart 中执行运行时类型检查? [英] How to perform runtime type checking in Dart?

问题描述

Dart 规范说明:

具体化的类型信息在运行时反映对象的类型，并且可能总是被动态类型检查构造(其他语言中instanceOf、casts、typecase等的类似物).

Reified type information reflects the types of objects at runtime and may always be queried by dynamic typechecking constructs (the analogs of instanceOf, casts, typecase etc. in other languages).

听起来不错，但没有类似 instanceof 的运算符.那么我们如何在 Dart 中执行运行时类型检查呢?有可能吗?

Sounds great, but there is no instanceof-like operator. So how do we perform runtime type-checking in Dart? Is it possible at all?

推荐答案

instanceof-operator 在 Dart 中称为 is.该规范对普通读者并不完全友好，因此现在最好的描述似乎是 http://www.dartlang.org/articles/optional-types/.

The instanceof-operator is called is in Dart. The spec isn't exactly friendly to a casual reader, so the best description right now seems to be http://www.dartlang.org/articles/optional-types/.

这是一个例子:

class Foo { }

main() {
  var foo = new Foo();
  if (foo is Foo) {
    print("it's a foo!");
  }
}

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