javascript - vue中如何初始化数组子元素

Question

我目前正在尝试使用 Vue 实现数组读取:

{{ this.locations[this.record.carton.LocationID - 1].Location }}

虽然代码本身在运行时工作正常，但在首次加载时会抛出以下错误:

app.js:55125 [Vue warn]: Error in render: "TypeError: Cannot read properties of undefined (reading 'Location')"

app.js:56401 TypeError: Cannot read properties of undefined (reading 'Location')
    at Proxy.render (app.js:49569:28)
    at VueComponent.Vue._render (app.js:58068:22)
    at VueComponent.updateComponent (app.js:58580:21)
    at Watcher.get (app.js:58994:25)
    at new Watcher (app.js:58983:12)
    at mountComponent (app.js:58587:3)
    at VueComponent.Vue.$mount (app.js:63593:10)
    at VueComponent.Vue.$mount (app.js:66507:16)
    at init (app.js:57639:13)
    at merged (app.js:57824:5)

我尝试像这样初始化 Location 的值，但似乎没有帮助

return {
     data() {
        return {
            locations: {
                Location: ''
            },
        }
     }
 }

Answer 1

解决问题的通用方法是设置默认值或防护或两者都设置。

默认 - 就像您尝试过的那样，除了数组之外，并注意索引表达式计算出默认索引...

return {
   data() {
      return {
        locations: [{ Location: '' }],
        record: { carton: { LocationID: 1 } }
      }
   }
 }

但这似乎有点做作且脆弱。另一种方法是使用 v-if 保护标记...

<div v-if="record && record.carton && locations && record.carton.LocationID - 1 < locations.length">
  {{ locations[record.carton.LocationID - 1].Location }}
</div>

该表达式涉及的内容足以保证将其放入方法中。