Ways to store information using VueJS lifecycle hooks

I am currently working on setting a data property using the created lifecycle hook within my component. The issue I'm encountering is receiving a

"TypeError: Cannot read property 'summary' of undefined"
in the console as I run the code. This error indicates that the template is handling forecastData as an empty object defined in the data property, rather than the populated object from created. Upon removing the data property altogether, the console displays
TypeError: Cannot read property 'currently' of undefined
. It seems like I have overlooked something fundamental here.

<template>
  <div>
    <p>
      <router-link to="/">Back to places</router-link>
    </p>
    <h2>{{forecastData.currently.summary}}</h2>
    <router-link :to="{ name: 'forecast' }">Forecast</router-link>
    <router-link :to="{ name: 'alerts' }">Alerts</router-link>
    <hr>
    <router-view></router-view>
  </div>
</template>

<script>
  export default {
    name: 'CurrentWeather',
    data () {
      return {
        forecastData: {}
      }
    },
    created: function () {
      this.$http.get('/api/forecast/boston').then((response) => {
        this.forecastData = response.data;
      }, (err) => {
        console.log(err)
      });
    }
  }
</script>

<style scoped>
</style>

Answer №1

If you are setting the data asynchronously, it may not exist when the object is initially mounted. This can lead to the forecastData.currently.summary property being undefined and causing an error.

To prevent this error, consider using a conditional rendering with a v-if.

<h2 v-if="forecastData.currently">{{forecastData.currently.summary}}</h2>

Alternatively, you can initialize the summary property as null in your data setup.

data () {
  return {
    forecastData: {
        summary: null
    }
  }
},

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