联合类型未在流类型中正确推断

Question

flowtype 无法识别以下给定类型，当我将它们用作如下函数的参数时：

/* @flow */

type Action =
    { type: "SELECT", componentToSelect: string }
    | { type: "UPDATE", componentToUpdate: string };

function dispatch(action: Action) {
  console.log(action.componentToSelect);
}
dispatch({
   type: "SELECT",
   componentToSelect: "anything"
});

报错信息如下：

componentToSelect. Property not found in object type

代码在线here

Answer 1

dispacth 函数需要一个 Action，但无法确定该 action 是否具有属性 componentToSelect。我应该先检查类型。

function dispatch(action: Action) {
  if (action.type === 'SELECT')
    console.log(action.componentToSelect);
}

查看online

联合类型未在流类型中正确推断

Union Types are not inferred properly in flowtype

javascript

redux

flowtype