javascript - 如何将项目推送到 Vuejs 中数据对象的数组中？Vue 似乎没有关注 .push() 方法

Question

我正在尝试将对象添加到我在 Vue 实例数据对象中声明的数组中。我可以在状态的购买对象中设置值，但是当我将数据推送到订单队列数组时，不会填充空数组。函数被触发，但数组没有更新。

这是我的表格：

<form
  v-on:submit.prevent="queuePurchase"
  class="form-inline row"
  id="order-creation-form"
  method="POST"
>

  @csrf
  <autocomplete-field
    sizing="col-xs-12 col-sm-3 col-md-3"
    name="customer"
    label="Customer"
    :data="{{ json_encode($customers) }}"
    v-on:setcustomer="setCustomer($event)"
  ></autocomplete-field>

  <div class="col-xs-12 col-sm-3 col-md3 form-group d-flex flex-column align-items-start">
    <label for="phone">Product</label>
    <select
      v-model="purchase.product"
      class="form-control w-100"
      name="product"
      aria-describedby="productHelpBlock"
      required
    >
      @foreach ($products as $product)
        <option :value="{{ json_encode($product) }}">
          {{ $product->name }}
        </option>
      @endforeach
    </select>
    <small id="productHelpBlock" class="form-text text-muted">
      Select a product
    </small>
  </div>

  <div class="col-xs-12 col-sm-3 col-md-3 form-group d-flex flex-column align-items-start">
    <label for="phone">Quantity</label>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      class="form-control w-100"
      aria-describedby="productHelpBlock"
      required
    >
    <small id="productHelpBlock" class="form-text text-muted">
      Product quantity
    </small>
  </div>

  <div class="form-group">
    <button type="submit" class="btn btn-success icon-button d-flex">
      <i class="material-icons">add</i>
      <span>&nbsp;&nbsp;  Q U E U E</span>
    </button>
  </div>
</form>

这是我的javascript：

require("./bootstrap");
window.Vue = require("vue");

Vue.component("queue-table", require('./components/QueueTable.vue'));
Vue.component("autocomplete-field", require('./components/AutocompleteField.vue'));

const purchaseApp = new Vue({
    el: "#purchase-app",

    data() {
        return {
            queue: [],
            purchase: {
                product: null,
                customer: null,
                quantity: null
            }
        }
    },

    methods: {
        setCustomer: function(customerObj) {
            this.purchase.customer = customerObj;
        },

        queuePurchase: function() {
            this.queue.push( this.purchase );
        }
    }
});

有人可以解释一下它发生的原因和原因吗？

Answer 1

该push()方法应该将purchase对象添加到queue数组中，但正如@FK82 在他的评论中指出的那样，push()是向同一个purchase对象添加多个引用。这意味着如果您通过增加 来更改对象，quantity则会更新 eachpurchase的属性。quantity

您可以在这里尝试一下：

const exampleComponent = Vue.component("example-component", {
  name: "exampleComponent",
  template: "#example-component",
  data() {
    return {
      queue: [],
      purchase: {
        product: null,
        customer: null,
        quantity: null
      }
    };
  },
  methods: {
    queuePurchase() {
      this.queue.push( this.purchase );
    }
  }
});

const page = new Vue({
  name: "page",
  el: ".page",
  components: {
    "example-component": exampleComponent
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.2.4/vue.min.js"></script>
<template id="example-component">
  <div>
    <p>The Queue has {{ this.queue.length }} items.</p>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      placeholder="Quantity"
    >
    <button @click="queuePurchase">
      Add to Queue
    </button>
    <pre>{{ JSON.stringify(this.queue, null, 2) }}</pre>
  </div>
</template>

<div class="page">
  <example-component></example-component>
</div>

尝试使用扩展运算符或使用扩展运算符创建浅拷贝，而不是push()对同一对象的引用。这是一个使用扩展运算符然后将副本复制到 的示例：purchaseObject.assign({}, this.purchase)push()queue

const exampleComponent = Vue.component("example-component", {
  name: "exampleComponent",
  template: "#example-component",
  data() {
    return {
      queue: [],
      purchase: {
        product: null,
        customer: null,
        quantity: null
      }
    };
  },
  methods: {
    queuePurchase() {
      this.queue.push({...this.purchase});
    }
  }
});

const page = new Vue({
  name: "page",
  el: ".page",
  components: {
    "example-component": exampleComponent
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.2.4/vue.min.js"></script>
<template id="example-component">
  <div>
    <p>The Queue has {{ this.queue.length }} items.</p>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      placeholder="Quantity"
    >
    <button @click="queuePurchase">
      Add to Queue
    </button>
    <pre>{{ JSON.stringify(this.queue, null, 2) }}</pre>
  </div>
</template>

<div class="page">
  <example-component></example-component>
</div>