112 lines
2.3 KiB
Markdown
112 lines
2.3 KiB
Markdown
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---
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id: 587d7db2367417b2b2512b89
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title: 使用 Mixin 在不相關對象之間添加共同行爲
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challengeType: 1
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forumTopicId: 301331
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dashedName: use-a-mixin-to-add-common-behavior-between-unrelated-objects
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---
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# --description--
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正如你所見，行爲是可以通過繼承來共享的。 然而，在有些情況下，繼承不是最好的解決方案。 繼承不適用於不相關的對象，比如 `Bird` 和 `Airplane`。 雖然它們都可以飛行，但是 `Bird` 並不是一種 `Airplane`，反之亦然。
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對於不相關的對象，更好的方法是使用 <dfn>mixins</dfn>。 mixin 允許其他對象使用函數集合。
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```js
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let flyMixin = function(obj) {
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obj.fly = function() {
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console.log("Flying, wooosh!");
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}
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};
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```
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`flyMixin` 能接受任何對象，併爲其提供 `fly` 方法。
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```js
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let bird = {
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name: "Donald",
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numLegs: 2
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};
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let plane = {
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model: "777",
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numPassengers: 524
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};
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flyMixin(bird);
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flyMixin(plane);
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```
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這裏的 `flyMixin` 接收了`bird` 和 `plane` 對象，然後將 `fly` 方法分配給了每一個對象。 現在 `bird` 和 `plane` 都可以飛行了：
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```js
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bird.fly();
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plane.fly();
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```
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控制檯將顯示字符串 `Flying, wooosh!` 兩次，每 `.fly()` 調用都會顯示。
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注意觀察 mixin 是如何允許相同的 `fly` 方法被不相關的對象 `bird` 和 `plane` 重用的。
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# --instructions--
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創建一個名爲 `glideMixin` 的 mixin，並定義一個 `glide` 方法。 然後使用 `glideMixin` 來給 `bird` 和 `boat` 賦予滑行（glide）的能力。
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# --hints--
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你應該聲明一個變量名爲 `glideMixin` 的函數。
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```js
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assert(typeof glideMixin === 'function');
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```
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你應該在 `bird`上使用 `glideMixin`，以提供 `glide` 方法。
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```js
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assert(typeof bird.glide === 'function');
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```
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你應該在 `boat` 上使用 `glideMixin`，以爲其提供 `glide` 方法。
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```js
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assert(typeof boat.glide === 'function');
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```
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# --seed--
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## --seed-contents--
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```js
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let bird = {
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name: "Donald",
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numLegs: 2
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};
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let boat = {
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name: "Warrior",
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type: "race-boat"
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};
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// Only change code below this line
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```
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# --solutions--
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```js
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let bird = {
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name: "Donald",
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numLegs: 2
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};
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let boat = {
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name: "Warrior",
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type: "race-boat"
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};
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function glideMixin (obj) {
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obj.glide = () => 'Gliding!';
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}
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glideMixin(bird);
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glideMixin(boat);
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```
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