2018-10-10 22:03:03 +00:00
|
|
|
|
---
|
|
|
|
|
id: 587d7db2367417b2b2512b89
|
2021-03-15 03:20:39 +00:00
|
|
|
|
title: 使用 Mixin 在不相关对象之间添加共同行为
|
2018-10-10 22:03:03 +00:00
|
|
|
|
challengeType: 1
|
2020-08-04 07:15:28 +00:00
|
|
|
|
forumTopicId: 301331
|
2021-01-13 02:31:00 +00:00
|
|
|
|
dashedName: use-a-mixin-to-add-common-behavior-between-unrelated-objects
|
2018-10-10 22:03:03 +00:00
|
|
|
|
---
|
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --description--
|
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
正如你所见,行为是可以通过继承来共享的。 然而,在有些情况下,继承不是最好的解决方案。 继承不适用于不相关的对象,比如 `Bird` 和 `Airplane`。 虽然它们都可以飞行,但是 `Bird` 并不是一种 `Airplane`,反之亦然。
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
对于不相关的对象,更好的方法是使用 <dfn>mixins</dfn>。 mixin 允许其他对象使用函数集合。
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
let flyMixin = function(obj) {
|
|
|
|
|
obj.fly = function() {
|
|
|
|
|
console.log("Flying, wooosh!");
|
|
|
|
|
}
|
|
|
|
|
};
|
|
|
|
|
```
|
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
`flyMixin` 能接受任何对象,并为其提供 `fly` 方法。
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
let bird = {
|
|
|
|
|
name: "Donald",
|
|
|
|
|
numLegs: 2
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
let plane = {
|
|
|
|
|
model: "777",
|
|
|
|
|
numPassengers: 524
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
flyMixin(bird);
|
|
|
|
|
flyMixin(plane);
|
|
|
|
|
```
|
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
这里的 `flyMixin` 接收了`bird` 和 `plane` 对象,然后将 `fly` 方法分配给了每一个对象。 现在 `bird` 和 `plane` 都可以飞行了:
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
|
|
|
|
```js
|
2021-03-15 03:20:39 +00:00
|
|
|
|
bird.fly();
|
|
|
|
|
plane.fly();
|
2020-08-04 07:15:28 +00:00
|
|
|
|
```
|
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
控制台将显示字符串 `Flying, wooosh!` 两次,每 `.fly()` 调用都会显示。
|
|
|
|
|
|
|
|
|
|
注意观察 mixin 是如何允许相同的 `fly` 方法被不相关的对象 `bird` 和 `plane` 重用的。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --instructions--
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
创建一个名为 `glideMixin` 的 mixin,并定义一个 `glide` 方法。 然后使用 `glideMixin` 来给 `bird` 和 `boat` 赋予滑行(glide)的能力。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --hints--
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
你应该声明一个变量名为 `glideMixin` 的函数。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
|
|
|
|
```js
|
2020-12-16 07:37:30 +00:00
|
|
|
|
assert(typeof glideMixin === 'function');
|
2018-10-10 22:03:03 +00:00
|
|
|
|
```
|
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
你应该在 `bird`上使用 `glideMixin`,以提供 `glide` 方法。
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
2018-10-10 22:03:03 +00:00
|
|
|
|
```js
|
2020-12-16 07:37:30 +00:00
|
|
|
|
assert(typeof bird.glide === 'function');
|
|
|
|
|
```
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
2021-03-15 03:20:39 +00:00
|
|
|
|
你应该在 `boat` 上使用 `glideMixin`,以为其提供 `glide` 方法。
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
```js
|
|
|
|
|
assert(typeof boat.glide === 'function');
|
2018-10-10 22:03:03 +00:00
|
|
|
|
```
|
2020-08-04 07:15:28 +00:00
|
|
|
|
|
2021-01-13 02:31:00 +00:00
|
|
|
|
# --seed--
|
|
|
|
|
|
|
|
|
|
## --seed-contents--
|
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
let bird = {
|
|
|
|
|
name: "Donald",
|
|
|
|
|
numLegs: 2
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
let boat = {
|
|
|
|
|
name: "Warrior",
|
|
|
|
|
type: "race-boat"
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
// Only change code below this line
|
|
|
|
|
```
|
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --solutions--
|
|
|
|
|
|
2021-01-13 02:31:00 +00:00
|
|
|
|
```js
|
|
|
|
|
let bird = {
|
|
|
|
|
name: "Donald",
|
|
|
|
|
numLegs: 2
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
let boat = {
|
|
|
|
|
name: "Warrior",
|
|
|
|
|
type: "race-boat"
|
|
|
|
|
};
|
|
|
|
|
function glideMixin (obj) {
|
|
|
|
|
obj.glide = () => 'Gliding!';
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
glideMixin(bird);
|
|
|
|
|
glideMixin(boat);
|
|
|
|
|
```
|