Issue detected: Props that are of type Object/Array must utilize a factory function in order to provide the default value

Question

Issue detected: Props that are of type Object/Array must utilize a factory function in order to provide the default value

I recently started using Vue-Cli3.0 and came across this interesting module for Vue.js called https://github.com/holiber/sl-vue-tree

It's a customizable draggable tree component for Vue.js, but I encountered an issue where it couldn't copy functions of objects.

I found the specific line causing the problem in the source code here: https://github.com/holiber/sl-vue-tree/blob/master/src/sl-vue-tree.js#L715

The solution was to use another module and modify the copy function. I used https://www.npmjs.com/package/clone for this purpose.

var clone = require('clone');

copy(entity) {
    return clone(entity)
},

By implementing this change, the object functions were copied correctly without any performance issues. However, I still encountered a console error message.

[Vue warn]: Invalid default value for prop "multiselectKey": Props with type Object/Array must use a factory function to return the default value.

found in

---> <SlVueTree>

I'm looking for a way to eliminate this error message. Any suggestions or insights would be greatly appreciated. Thank you for taking the time to read my question.

javascript typescript vue.js vuejs2

Answer 1

Answer №1

One way to define a factory function in props is shown below:

props: {
    exampleDefaultObject: {
        type: Object,
        default() {
            return {}
        }
    },
    exampleDefaultArray: {
        type: Array,
        default() {
            return []
        }
    }
},

Alternatively, you can achieve the same result in ES6 syntax:

props: {
    exampleDefaultObject: {
        type: Object,
        default: () => ({})
    },
    exampleDefaultArray: {
        type: Array,
        default: () => []
    }
},

(This explanation clarifies the error mentioned by individuals inquiring about 'props with type object/array must use a factory function to return the default value')

It's important to note that when returning an object within an es6 arrow function, it is necessary to use parentheses as demonstrated: () => ({}) rather than () => {}

Answer 2

One way to define a factory function in props is shown below:

props: {
    exampleDefaultObject: {
        type: Object,
        default() {
            return {}
        }
    },
    exampleDefaultArray: {
        type: Array,
        default() {
            return []
        }
    }
},

Alternatively, you can achieve the same result in ES6 syntax:

props: {
    exampleDefaultObject: {
        type: Object,
        default: () => ({})
    },
    exampleDefaultArray: {
        type: Array,
        default: () => []
    }
},

(This explanation clarifies the error mentioned by individuals inquiring about 'props with type object/array must use a factory function to return the default value')

It's important to note that when returning an object within an es6 arrow function, it is necessary to use parentheses as demonstrated: () => ({}) rather than () => {}

Answer 3

Answer №2

After reviewing the warning in your console, I have identified the error.

Check out this link for more information

Consider implementing the following solution:

multiselectKey: {
  type: [String, Array],
  default: function () {
    return ['ctrlKey', 'metaKey']
  },
  validator: function (value) {
    let allowedKeys = ['ctrlKey', 'metaKey', 'altKey'];
    let multiselectKeys = Array.isArray(value) ? value : [value];
    multiselectKeys = multiselectKeys.filter(keyName => allowedKeys.indexOf(keyName ) !== -1);
    return !!multiselectKeys.length;
  }
},

Remember to use a factory function to set the component's default value!

I hope this solution helps you resolve the issue.

Answer 4

After reviewing the warning in your console, I have identified the error.

Check out this link for more information

Consider implementing the following solution:

multiselectKey: {
  type: [String, Array],
  default: function () {
    return ['ctrlKey', 'metaKey']
  },
  validator: function (value) {
    let allowedKeys = ['ctrlKey', 'metaKey', 'altKey'];
    let multiselectKeys = Array.isArray(value) ? value : [value];
    multiselectKeys = multiselectKeys.filter(keyName => allowedKeys.indexOf(keyName ) !== -1);
    return !!multiselectKeys.length;
  }
},

Remember to use a factory function to set the component's default value!

I hope this solution helps you resolve the issue.

Answer 5

Answer №3

These specific scenarios call for a function to generate the default value, rather than an object or array:

obj_param:{
        type:Object,
        default:()=>({})
},
array_param:{
        type:Array,
        default:()=>[]
},

This approach is implemented for optimized performance, as the function is only invoked when necessary (when there is no existing value and the default is used), unlike if a direct value were utilized which would result in instantiation every time the component is employed.

Answer 6

These specific scenarios call for a function to generate the default value, rather than an object or array:

obj_param:{
        type:Object,
        default:()=>({})
},
array_param:{
        type:Array,
        default:()=>[]
},

This approach is implemented for optimized performance, as the function is only invoked when necessary (when there is no existing value and the default is used), unlike if a direct value were utilized which would result in instantiation every time the component is employed.

Answer 7

Answer №4

When working on my class component in TypeScript format, I came across a similar issue and was able to resolve it using the code below. Special thanks to Trick and Katinka for providing the solution!

@Prop({default(){return []}}) private markerList!: Array<markerType>;

Answer 8

When working on my class component in TypeScript format, I came across a similar issue and was able to resolve it using the code below. Special thanks to Trick and Katinka for providing the solution!

@Prop({default(){return []}}) private markerList!: Array<markerType>;

Issue detected: Props that are of type Object/Array must utilize a factory function in order to provide the default value

Answer №1

Answer №2

Answer №3

Answer №4

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