流，类型的破坏对象

Question

我无法找出输入这种类型的析构对象的语法

const { height: deviceHeight, width: deviceWidth } = Dimensions.get("window");

现在deviceHeight和deviceWidth被揭露，两者都应该是数字。

Answer 1

我想你想要这个：

const { height: deviceHeight, width: deviceWidth }: { height: number, width: number } = Dimensions.get("window");

您可以通过将其插入以下内容来正确输入deviceHeight和deviceWidth：

// @flow
const { height: deviceHeight, width: deviceWidth }: { height: number, width: number } = { height: 1, width: 2 };

function logString(str: string) {
  console.log(str);
}

logString(deviceHeight);

...给出了这个输出：

logString(deviceHeight);
          ^ Cannot call `logString` with `deviceHeight` bound to `str` because number [1] is incompatible with string [2].

（See it on flow.org）