💡 Vue Typescript State Management : We can do better than “isLoading” in 2022

Sorry for the clickbait title, but I needed your attention 👀 

Have you ever encountered code like this one :

new Vue({
  el: '#app',
  data () {
    return {
      info: null,
      loading: true,
      errored: false
    }
  },
  filters: {
    currencydecimal (value) {
      return value.toFixed(2)
    }
  },
  mounted () {
    axios
      .get('https://api.coindesk.com/v1/bpi/currentprice.json')
      .then(response => {
        this.info = response.data.bpi
      })
      .catch(error => {
        console.log(error)
        this.errored = true
      })
      .finally(() => this.loading = false)
  }
})

...

<div id="app">
  <h1>Bitcoin Price Index</h1>

  <section v-if="errored">
    <p>We're sorry, we're not able to retrieve this information at the moment, please try back later</p>
  </section>

  <section v-else>
    <div v-if="loading">Loading...</div>

    <div
      v-else
      v-for="currency in info"
      class="currency"
    >
      {{ currency.description }}:
      <span class="lighten">
        <span v-html="currency.symbol"></span>{{ currency.rate_float | currencydecimal }}
      </span>
    </div>

  </section>
</div>

It’s an example I found in the Vue documentation here https://vuejs.org/v2/cookbook/using-axios-to-consume-apis.html#Dealing-with-Errors

What if you have multiple things that could load, do you add a loading2 variable ? 👀

To solve this issue, you can use a variable for each async actions you have with this 4 “states” :

  • IDLE : the user didn’t trigger the action yet
  • WAITING : the action is ongoing
  • ERROR : there was an error
  • DONE : The action succeeded

Using an enum with the different states, and better naming, the code can be rewritten like this :

enum AsyncState {
  IDLE = 'IDLE',
  WAITING = 'WAITING',
  ERROR = 'ERROR',
  DONE = 'DONE',
}

new Vue({
  el: '#app',
  data () {
    return {
      info: null,

      AsyncState,
      currentPriceLoadState: AsyncState.WAITING,
    }
  },
  filters: {
    currencydecimal (value) {
      return value.toFixed(2)
    }
  },
  mounted () {
    axios
      .get('https://api.coindesk.com/v1/bpi/currentprice.json')
      .then(response => {
        this.info = response.data.bpi
        this.currentPriceLoadState = AsyncState.DONE
      })
      .catch(error => {
        console.log(error)
        this.currentPriceLoadState = AsyncState.ERROR
      })
  }
})

...

<div id="app">
  <h1>Bitcoin Price Index</h1>

  <div v-if="currentPriceLoadState === AsyncState.WAITING">Loading...</div>
  <section v-else-if="currentPriceLoadState === AsyncState.ERROR">
    <p>We're sorry, we're not able to retrieve this information at the moment, please try back later</p>
  </section>

  <section v-else>
    <div v-for="currency in info" class="currency">
      {{ currency.description }}:
      <span class="lighten">
        <span v-html="currency.symbol"></span>{{ currency.rate_float | currencydecimal }}
      </span>
    </div>

  </section>
</div>

With better naming and this simple enum, you can almost cover all the use cases where you need to load one or multiple things and manage errors ✨

If you want to manage different error messages, you can add another variable with an enum type like this :

enum CurrentPriceLoadErrors {
  INVALID_CURRENCY = 'INVALID_CURRENCY',
  API_LIMIT_REACHED = 'API_LIMIT_REACHED',
  DEFAULT = 'DEFAULT',
}

Tell me in the comment section if you like this trick or not, and if you have an even better technique !

And don’t forget to like and share this post if you liked it 💙

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