繼續看 Composition API 的 Reactive and toRefs。

Reactive

我們看上次的 ref 範例。

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<template>
  <div>
    <p>Space Left: {{ spaceLeft }} out of {{ capacity }}</p>
    <h2>Attending</h2>
    <ul>
      <li v-for="(name, index) in attending" :key="index">
        {{ name }}
      </li>
    </ul>
    <button @click="increaseCapacity()">Increase Capacity</button>
  </div>
</template>
<script>
import { ref, computed } from "vue";
export default {
  setup() {
    const capacity = ref(4);
    const attending = ref(["Tim", "Bob", "Joe"])

    const spaceLeft = computed(() => {
      return capacity.value - attending.value.length;
    });

    function increaseCapacity() {
      capacity.value++;
    }

    return { capacity, attending, spaceLeft, increaseCapacity };
  }
};
</script>

我們可以用 Reactive 把全部的 ref 統整成一個物件 event。
下面的程式跟上面運行結果是一樣的。

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<template>
  <div>
    <p>Space Left: {{ event.spaceLeft }} out of {{ event.capacity }}</p>
    <h2>Attending</h2>
    <ul>
      <li v-for="(name, index) in event.attending" :key="index">
        {{ name }}
      </li>
    </ul>
    <button @click="increaseCapacity()">Increase Capacity</button>
  </div>
</template>
<script>
import { reactive, computed } from "vue";
export default {
  setup() {
    const event = reactive({
      capacity: 4,
      attending: ["Tim", "Bob", "Joe"],
      spaceLeft: computed(() => {
        return event.capacity - event.attending.length;
      });
    });

    function increaseCapacity() {
      event.capacity++;
    }

    return { event, increaseCapacity };
  }
};
</script>

HTML 裡面每次都要使用 event.xxx 感覺很煩，在這裡我們就可以用 toRefs ，再把他拆開成個別物件。

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<template>
  <div>
    <p>Space Left: {{ spaceLeft }} out of {{ capacity }}</p>
    <h2>Attending</h2>
    <ul>
      <li v-for="(name, index) in attending" :key="index">
        {{ name }}
      </li>
    </ul>
    <button @click="increaseCapacity()">Increase Capacity</button>
  </div>
</template>
<script>
import { reactive, computed, toRefs } from "vue";
export default {
  setup() {
    const event = reactive({
      capacity: 4,
      attending: ["Tim", "Bob", "Joe"],
      spaceLeft: computed(() => {
        return event.capacity - event.attending.length;
      });
    });

    function increaseCapacity() {
      event.capacity++;
    }

    return { toRefs(event), increaseCapacity };
  }
};
</script>

參考資料