如何在ReasonML中扩展JS类 [英] How to extend JS class in ReasonML

问题描述

例如，我有一个 es6 类的类：

For example, I have an es6-like class:

class Foo {...}

我想扩展它：

class Bar扩展了Foo {...}

在 reason-react 文档中，我找到了示例，但我是不确定它是否适合我：

In reason-react documentation I found examples, but I'm not sure that it's appropriate for me:

let component = ReasonReact.reducerComponent "TodoAppRe";
let make _children => {
  ...component,
  initialState: fun () => {count: 0},
  <...>

但是当我尝试以这种方式编写代码时，我收到一个错误：

But when i try to write code in this style, i get an error:

let myclass unit => {
  ...mysuperclass,
    hello: fun () => {
      Js.log "FooBar";
    }
};

错误：未绑定记录字段更新

Error: Unbound record field update

（在本例中， mysuperclass 来自第三方js-library）。

(In this example mysuperclass is external from 3rd-party js-library).

也许我做错了什么？

推荐答案

让foo吧=> {... baz，quux：...} 不是继承的语法，它是组合的语法。具体来说，它采用 baz 记录值（不是对象）并更新其 quux 成员（不是方法）。

let foo bar => { ...baz, quux: ... } is not a syntax for inheritance, it's a syntax for composition. Specifically, it's taking the baz record value (not object) and updating its quux member (not method).

如果你想在Reason / BuckleScript中扩展JS类，首先要记住BuckleScript生成的代码与ES5向后兼容，因此你不需要使用巴贝尔。事实上，BuckleScript不直接支持扩展类。

If you want to extend a JS class in Reason/BuckleScript, first keep in mind that BuckleScript generates code that's backwards-compatible with ES5, so that you don't need to use Babel. In fact BuckleScript doesn't directly support extending a class.

但是，你可以使用BuckleScript的<$在原始源代码中包含原始JavaScript c $ c> [%% bs.raw] 属性（ https://bucklescript.github.io/bucklescript/Manual.html#_embedding_raw_js_code_as_statements ）：

But, you can include raw JavaScript in your Reason source code using BuckleScript's [%%bs.raw] attribute ( https://bucklescript.github.io/bucklescript/Manual.html#_embedding_raw_js_code_as_statements ):

/* MyProject_Animal.re */

[%%bs.raw {|

// Dummy class for example:
class Animal {
  speak() {}
}

// or:
// import Animal from "somewhere";

class Dog extends Animal {
  _name;

  constructor(name) {
    super();
    this._name = name;
  }

  speak() {
    console.log(`${this._name} says woof!!`);
    super.speak();
  }
}
|}];

然后你可以写一个绑定到 Dog 下面代码中的类：

And then you can write a binding to the Dog class in the code below that:

module Animal_Dog = {
  type t;

  [@bs.new] external make: string => t = "Dog";
  /* Need this to ensure correct usage in other modules */
  let make = make;

  [@bs.send] external speak: t => unit = "";
};

let spot = Animal_Dog.make("Spot");
Animal_Dog.speak(spot);

但是，请记住，自从这个ES2015以来，如果你想要它，你将需要通过Babel运行它与ES2015之前的浏览器向后兼容。

But, remember that since this ES2015, you will need to run it through Babel if you want it to be backwards-compatible with pre-ES2015 browsers.

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