Warning from Vue: Steer clear of directly changing a prop as it will be replaced whenever the parent component undergoes re-rendering

Question

Warning from Vue: Steer clear of directly changing a prop as it will be replaced whenever the parent component undergoes re-rendering

I've been diving into Vue.js, but I'm encountering an issue. Every time I try to click on the "edit age" or "change my name" button, I get the following error message.

[Vue warn]: Avoid mutating a prop directly because the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "myName"

[Vue warn]: Avoid mutating a prop directly because the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "userAge"

Check out this code snippet below.

https://codesandbox.io/s/k2197nr4o3

Please help me figure out what might be wrong in this piece of code.

javascript vue.js vuejs2 vue-component vuex

Answer 1

Answer №1

It appears that you are attempting to directly alter the props properties.

For instance:

props: { name: 'something' }
methods: { 
 change_name(new_name) {
   this.name = new_name
 }
}

This approach is not recommended and may result in a lack of reactivity.

Instead, consider using parent-child communication. When you need to modify a prop, emit an event to the parent component. The updated example should look like this:

props: { name: 'something' }
methods: { 
 change_name(new_name) {
   this.$emit('name-updated', new_name)
 }
}

In the parent component, listen for that event to update the prop being passed:

<child-component :name="name" @name-updated="name = $event" />

Alternatively, my preferred method is to use the .sync modifier. In this case, the parent component would be:

<child-component :name.sync="name" />

and the method in the child component:

 change_name(new_name) {
   this.$emit('update:name', new_name)
 }

If the components are not related in a parent-child hierarchy, consider exploring Vue.js Event Bus or Vuex.

Answer 2

It appears that you are attempting to directly alter the props properties.

For instance:

props: { name: 'something' }
methods: { 
 change_name(new_name) {
   this.name = new_name
 }
}

This approach is not recommended and may result in a lack of reactivity.

Instead, consider using parent-child communication. When you need to modify a prop, emit an event to the parent component. The updated example should look like this:

props: { name: 'something' }
methods: { 
 change_name(new_name) {
   this.$emit('name-updated', new_name)
 }
}

In the parent component, listen for that event to update the prop being passed:

<child-component :name="name" @name-updated="name = $event" />

Alternatively, my preferred method is to use the .sync modifier. In this case, the parent component would be:

<child-component :name.sync="name" />

and the method in the child component:

 change_name(new_name) {
   this.$emit('update:name', new_name)
 }

If the components are not related in a parent-child hierarchy, consider exploring Vue.js Event Bus or Vuex.

Answer 3

Answer №2

Consider using a calculated value instead. For instance, in your UserEdit.vue file:

In your template section:

<p>User's Current Age: {{ calculatedUserAge }}</p>

In your script section:

methods: {
    updateUserAge() {
        this.calculatedUserAge = 30;
    }
},
computed: {
    calculatedUserAge: {
      get() {
        return this.currentUserAge;
      },
      set(v) {
        this.$emit("ageUpdated", v);
      }
    }
}

Answer 4

Consider using a calculated value instead. For instance, in your UserEdit.vue file:

In your template section:

<p>User's Current Age: {{ calculatedUserAge }}</p>

In your script section:

methods: {
    updateUserAge() {
        this.calculatedUserAge = 30;
    }
},
computed: {
    calculatedUserAge: {
      get() {
        return this.currentUserAge;
      },
      set(v) {
        this.$emit("ageUpdated", v);
      }
    }
}

Warning from Vue: Steer clear of directly changing a prop as it will be replaced whenever the parent component undergoes re-rendering

Answer №1

Answer №2

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