The Vue Application has encountered a persistent loop caused by interdependent variables, presenting a challenging logic problem

Question

The Vue Application has encountered a persistent loop caused by interdependent variables, presenting a challenging logic problem

I have been developing a Vue application that allows users to convert between fiat currency and cryptocurrencies. You can try the app out for yourself here: Demo.

One interesting feature of the app is that the conversion calculation happens automatically in real-time as you type, displaying the result in the other input box. However, I've encountered an issue where the calculation only occurs when changes are made to the input variables.

In addition to updating on user input, I also want the calculation to happen when a different option is selected from the dropdown menu.

I've been struggling to find a solution without creating an endless loop in the process.

My initial attempt to solve the problem can be found here: codepen.

From my understanding, the current issue arises because:

...input1 changes -> watch input1 called -> watch input1 modifies 
input2 -> watch input2 called -> watch input2 modifies input1....

This creates an infinite loop situation. It seems there's a specific aspect of Vue.js that I haven't mastered yet to address this particular challenge.

Thank you for your help,

javascript vue.js vuex vuetify.js

Answer 1

Answer №1

To achieve synchronization between two input fields, utilize the @input event listener. This means that when you modify the value in one input field, it will automatically update the value in the other input field.

<template>
  <div>
    <input v-model="value1" @input="update2"> 
    to 
    <input v-model="value2" @input="update1">
  </div>
</template>

<script>
const mul = 1.5;
export default {
  data: () => ({
    value1: null,
    value2: null
  }),
  methods: {
    update1() {
      this.value1 = this.value2 / mul;
    },
    update2() {
      this.value2 = this.value1 * mul;
    }
  }
};
</script>

If you prefer using watch for this functionality, remember to add an additional check to prevent an endless loop:

watch: {
  value1(val) {
    const tmp = val * mul;
    if (tmp !== this.value2) {
      this.value2 = tmp;
    }
  },
  value2(val) {
    const tmp = val / mul;
    if (tmp !== this.value1) {
      this.value1 = tmp;
    }
  }
},

It's important to note that while multiplying by x and then dividing by x should yield the same number mathematically, working with floats (javascript's number type) introduces potential exceptions like NaN or rounding issues. Therefore, the simpler and recommended approach is using the input event-listener method.

Answer 2

To achieve synchronization between two input fields, utilize the @input event listener. This means that when you modify the value in one input field, it will automatically update the value in the other input field.

<template>
  <div>
    <input v-model="value1" @input="update2"> 
    to 
    <input v-model="value2" @input="update1">
  </div>
</template>

<script>
const mul = 1.5;
export default {
  data: () => ({
    value1: null,
    value2: null
  }),
  methods: {
    update1() {
      this.value1 = this.value2 / mul;
    },
    update2() {
      this.value2 = this.value1 * mul;
    }
  }
};
</script>

If you prefer using watch for this functionality, remember to add an additional check to prevent an endless loop:

watch: {
  value1(val) {
    const tmp = val * mul;
    if (tmp !== this.value2) {
      this.value2 = tmp;
    }
  },
  value2(val) {
    const tmp = val / mul;
    if (tmp !== this.value1) {
      this.value1 = tmp;
    }
  }
},

It's important to note that while multiplying by x and then dividing by x should yield the same number mathematically, working with floats (javascript's number type) introduces potential exceptions like NaN or rounding issues. Therefore, the simpler and recommended approach is using the input event-listener method.

The Vue Application has encountered a persistent loop caused by interdependent variables, presenting a challenging logic problem

Answer №1

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