javascript - Flowtype:不安全的实例变量访问

Question

/* @flow */

class Foo {
    blah: string;
    bar: string;
    constructor(blah: string, bar?: string) {
            this.blah = blah
            if (bar) {
                this.bar = bar
            }
    }
}

const foo = new Foo('okok')
foo.bar

https://flowtype.org/try/#0PQKgBAAgZgNg9gdzCYAoVBjGBDAzrsAMTjjAG9UBIAI2wCcAuMXAFzoEsA7AcwG5UAvugxxOrMFBJgAvGE4BTJMTgAKAJSpJcAHS06QA

这不会引发流类型错误吗？

编辑:

这可能回答我的问题...

https://flowtype.org/docs/nullable-types.html#undefined-values-and-optional-types

Undefined Values and Optional Types Undefined values, just like null, can cause issues too. Unfortunately, undefined values are ubiquitous in JavaScript and it is hard to avoid them without severely affecting the usability of the language. For example, arrays can have holes for elements; object properties can be dynamically added and removed. Flow ignores the possibility of undefined resulting from object property and array element accesses. Being stricter would force the programmer to do undefined checks (like null checks) on each dereference of an array element or object property to get anything useful done.

However, Flow does detect undefined local variables and return values, and it considers optional parameters and properties to possibly be undefined. As such, uses of these types must be guarded by undefined checks to avoid errors.

Answer 1

当前 (v0.36) 类字段不受 Flow 确保

class Foo {
  bar: string;
}

new Foo().bar // no error