[Vue-rx] Switch to a Function which Creates Observables with Vue.js and Rxjs

Wrapping the creation of an Observable inside of a Function allows you delay the creation of the Observable until it is needed. This becomes really important when the Observable is created from a Promise due to the way Promises execute on creation.

Current Code:

<template>
  <section class="section">
    <button class="button" v-stream:click="click$">Click</button>
    <h2>
      {{name$}}
    </h2>
    <img v-stream:error="imageError$" :src="image$" alt="">
  </section>
</template>

<script>
import { from, merge } from 'rxjs';
import { switchMap, pluck, map, mapTo } from 'rxjs/operators';

export default {
  name: 'app',
  domStreams: ['click$', 'imageError$'],
  subscriptions() {

    const person$ = from(
      this.$http.get(
        "https://starwars.egghead.training/people/1"
      )
    ).pipe(
      pluck('data')
    )

    const luke$ = this.click$.pipe(
      switchMap(() => person$)
    )

    const name$ = luke$.pipe(
      pluck('name')
    )

    const loadImage$ = luke$.pipe(
      pluck('image'),
      map(src => `https://starwars.egghead.trainin/${src}` )
    )

    const failImage$ =  this.imageError$
    .pipe(
      mapTo(`http://via.placeholder.com/400x400`)
    )

    const image$ = merge(
      loadImage$,
      failImage$
    )

    return {
      name$,
      image$
    }
  }
};
</script>

The highlight part of code will be run once page loaded. So it means before the button was clicked, we already send a network request.

To defer the network request, we can do:

<template>
  <section class="section">
    <button class="button" v-stream:click="click$">Click</button>
    <h2>
      {{name$}}
    </h2>
    <img v-stream:error="imageError$" :src="image$" alt="">
  </section>
</template>

<script>
import { from, merge } from 'rxjs';
import { switchMap, pluck, map, mapTo } from 'rxjs/operators';

export default {
  name: 'app',
  domStreams: ['click$', 'imageError$'],
  subscriptions() {

    const loadPerson = (url) => from(
      this.$http.get(
        url
      )
    ).pipe(
      pluck('data')
    )

    const luke$ = this.click$.pipe(
      mapTo("https://starwars.egghead.training/people/1"),
      switchMap((url) => loadPerson(url))
    );

    const name$ = luke$.pipe(
      pluck('name')
    )

    const loadImage$ = luke$.pipe(
      pluck('image'),
      map(src => `https://starwars.egghead.training/${src}` )
    )

    const failImage$ =  this.imageError$
    .pipe(
      mapTo(`http://via.placeholder.com/400x400`)
    )

    const image$ = merge(
      loadImage$,
      failImage$
    )

    return {
      name$,
      image$
    }
  }
};
</script>