Preserving reactivity while swapping an item in Vue 3 using the composition API

Question

Preserving reactivity while swapping an item in Vue 3 using the composition API

I am looking to update my object while maintaining reactivity. The variable selectedTime is a Date object, and the function substractMonths will return a new Date object.

<span
   class="calendar__pickable__chevron"
   @click="selectedTime = substractMonths(1, selectedTime)"
   >
   <span>
      <font-awesome-icon icon="chevron-left" />
   </span>
</span>

However, I am facing an issue where Vue 3 is unable to detect the replacement of the object when this operation is performed.

Is there a way to resolve this? (I have used

const selectedTime = ref(new Date())

to create a reactive object).

https://i.sstatic.net/DBDDh.png

The substract function does indeed return a new Date object.

Excerpt from code: https://gist.github.com/SirMishaa/efb0efe74c6355aabbcb853f7650c22f

My goal is simply to run a function that returns a new date, and replace my selectedTime with the result of that function.

javascript typescript vue.js vuejs3

Answer 1

Answer №1

After significant effort, I have successfully resolved the issue and am excited to share the solution.

To illustrate, I have created a simple example: https://codesandbox.io/s/wandering-paper-o952k?file=/src/App.vue

<template>
  <h1>{{ currentTime.toString() }}</h1>
  <button @click="currentTime = addMonths(1, currentTime)">
    Add one month
  </button>
</template>

function addMonths(numberOfMonths, currentTime) {
  const x = currentTime.getDate();
  currentTime.setMonth(currentTime.getMonth() + numberOfMonths);
  console.log(`Function has been called with : ${currentTime}`);
  if (currentTime.getDate() !== x) {
    currentTime.setDate(0);
  }
  return currentTime;
}

Upon investigation, it appears that Vue is unable to detect the change due to returning an object with the same reference as the old object. The key to resolving this issue lies in creating a new object to facilitate change detection.

Instead of using return currentTime;, opt for something similar to return new Date(currentTime) which should yield the desired results.

I hope this explanation proves helpful after my extensive search for a solution.

Answer 2

After significant effort, I have successfully resolved the issue and am excited to share the solution.

To illustrate, I have created a simple example: https://codesandbox.io/s/wandering-paper-o952k?file=/src/App.vue

<template>
  <h1>{{ currentTime.toString() }}</h1>
  <button @click="currentTime = addMonths(1, currentTime)">
    Add one month
  </button>
</template>

function addMonths(numberOfMonths, currentTime) {
  const x = currentTime.getDate();
  currentTime.setMonth(currentTime.getMonth() + numberOfMonths);
  console.log(`Function has been called with : ${currentTime}`);
  if (currentTime.getDate() !== x) {
    currentTime.setDate(0);
  }
  return currentTime;
}

Upon investigation, it appears that Vue is unable to detect the change due to returning an object with the same reference as the old object. The key to resolving this issue lies in creating a new object to facilitate change detection.

Instead of using return currentTime;, opt for something similar to return new Date(currentTime) which should yield the desired results.

I hope this explanation proves helpful after my extensive search for a solution.

Preserving reactivity while swapping an item in Vue 3 using the composition API

Answer №1

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