Tips for maintaining data reactivity while transmitting it to a function

Question

Tips for maintaining data reactivity while transmitting it to a function

Consider the following setup for my component:

<script setup lang="ts">
interface FileMetadata {
  owner: string,
  location: string,
  size: number,
  // And around 50 mores...
}

interface File {
  fileName: string,
  metadata: FileMetadata
}

const file = defineModel<File>({ required: true });

const buildControls = (metadata: FileMetadata) => {
  return [
    {
      label: 'Owner',
      model: metadata.owner,  // Is this correct?
      type: 'text'
    },
    {
      label: 'Location',
      model: metadata.location,  // Is this correct?
      type: 'text'
    },
    {
      label: 'Size',
      model: metadata.size,  // Is this correct?
      type: 'number'
    },
    // And around 50 mores...
  ];
};

const controls = buildControls(file.value.metadata);  // The value is already unpacked here
</script>

<template>
  <div v-for=(item, idx) in controls>
    <v-text-field v-model="item[idx].model" :label="item[idx].label" :type="item[idx].type" />
  </div>
</template>

This component receives a File object through its v-model and displays a view for users to edit its metadata. Whenever the model changes (a different file is passed), the values of the text fields should update accordingly. Similarly, any changes made by users in the text fields should also reflect in the model. This behavior represents a two-way binding.

The view renders correctly, but I'm encountering an issue where I cannot alter the values in the text fields (they revert to their initial values when losing focus). I suspect this happens because the file is already unpacked when the buildControls() function is invoked, causing a loss of reactivity. However, if I refrain from unpacking it (by not accessing its .value), I lose access to its metadata attribute.

If I try to make controls reactive by using

const controls = reactive(buildControls(file.value.metadata));

then I am able to modify the values in the text fields, but the file model does not update accordingly.

In my understanding, the value of the model key should be a Ref object. However, I seem to be unable to achieve this.

One potential solution could involve storing only the key name of the FileMetadata instead of the entire object in the model key. This way, it can be accessed later in the template as file.metadata[item.model]. Nevertheless, I find this approach less than ideal. Why shouldn't I be able to simply store an object instead?

What error have I made in this setup? How can I ensure the data maintains its reactivity as intended?

typescript vue.js vuejs3 nuxt.js vuetify.js

Answer 1

Answer №1

controls does not exhibit reactivity and must be modified:

const controls = ref();
...
controls.value = buildControls(...);

Alternatively:

const controls = reactive(buildControls(...));

The issue lies in the fact that controls is designed for two-way synchronization with file, making implementation challenging due to its structure. The challenge of storing mixed mutable and static data is a common one, with insufficient reasons to keep them unified.

If the component is expected to emit changes to file to a parent based on modifications to v-model="item[idx].model", tracking specific changes can be problematic.

A list of metadata keys that both static and mutable data can utilize should be established. It is recommended to maintain static field data as a constant, allowing types to be derived for enhanced type safety (implementation of ValidateKeys can be observed here):

const fileMetaFields = {
  owner: {
    label: 'Owner',
    type: 'text'
  },
  ...
}

type FileMetaKeys = keyof typeof fileMetaFields;

type FileMeta = ValidateKeys<FileMetaKeys, {
  owner: string,
  ...
}

Additional utility types can be created to automatically translate type: 'text' to string.

If the component is meant to update the parent's model, it may not require its own state. The use of v-model in v-text-field restricts the ways in which the model can be updated, necessitating desugaring:

  function updateModelField({ key, value }) {
    emit('update:modelValue', {
      ...file.value,
      metadata: {
        ...file.value.metadata
        [key]: value
      },
    });
  }

  ...

  <div v-for=(field, key) in fileMetaFields>
    <v-text-field
      :label="field.label"
      :modelValue="file.value.metadata[key]" />
      @update:modelValue="updateModelField({ key, value: $event })"
      ...

This highlights the challenge with file. To prevent the model prop from being mutated in a child and achieve Vue's two-way binding in a parent, the entire object must be cloned to modify one field. This inefficiency can be mitigated by providing the child with only the necessary data (metadata instead of file) and updating file in the parent using a custom event instead of v-model.

Therefore, in the child:

  const props = defineProps<{ data: FileMeta }>();

  function updateModelField({ key, value }) {
    emit('update:field', { key, value });
  }

In the parent:

<FileMetaForm
  :data="file.metadata"
  @update:field="file.metadata[$event.key] = $event.value"
>

Answer 2

controls does not exhibit reactivity and must be modified:

const controls = ref();
...
controls.value = buildControls(...);

Alternatively:

const controls = reactive(buildControls(...));

The issue lies in the fact that controls is designed for two-way synchronization with file, making implementation challenging due to its structure. The challenge of storing mixed mutable and static data is a common one, with insufficient reasons to keep them unified.

If the component is expected to emit changes to file to a parent based on modifications to v-model="item[idx].model", tracking specific changes can be problematic.

A list of metadata keys that both static and mutable data can utilize should be established. It is recommended to maintain static field data as a constant, allowing types to be derived for enhanced type safety (implementation of ValidateKeys can be observed here):

const fileMetaFields = {
  owner: {
    label: 'Owner',
    type: 'text'
  },
  ...
}

type FileMetaKeys = keyof typeof fileMetaFields;

type FileMeta = ValidateKeys<FileMetaKeys, {
  owner: string,
  ...
}

Additional utility types can be created to automatically translate type: 'text' to string.

If the component is meant to update the parent's model, it may not require its own state. The use of v-model in v-text-field restricts the ways in which the model can be updated, necessitating desugaring:

  function updateModelField({ key, value }) {
    emit('update:modelValue', {
      ...file.value,
      metadata: {
        ...file.value.metadata
        [key]: value
      },
    });
  }

  ...

  <div v-for=(field, key) in fileMetaFields>
    <v-text-field
      :label="field.label"
      :modelValue="file.value.metadata[key]" />
      @update:modelValue="updateModelField({ key, value: $event })"
      ...

This highlights the challenge with file. To prevent the model prop from being mutated in a child and achieve Vue's two-way binding in a parent, the entire object must be cloned to modify one field. This inefficiency can be mitigated by providing the child with only the necessary data (metadata instead of file) and updating file in the parent using a custom event instead of v-model.

Therefore, in the child:

  const props = defineProps<{ data: FileMeta }>();

  function updateModelField({ key, value }) {
    emit('update:field', { key, value });
  }

In the parent:

<FileMetaForm
  :data="file.metadata"
  @update:field="file.metadata[$event.key] = $event.value"
>

Answer 3

Answer №2

To maintain data reactivity, utilize the computed property in your code like so:

<script setup lang="ts">
interface FileMetadata {
  owner: string,
  location: string,
  size: number,
  // Plus approximately 50 more properties...
}

interface File {
  fileName: string,
  metadata: FileMetadata
}

const file = defineModel<File>({ required: true });

const buildControls = (metadata: FileMetadata) => {
  return [
    {
      label: 'Owner',
      model: metadata,  // Is this the right approach?
      type: 'text',
      field: "owner"
    },
    {
      label: 'Location',
      model: metadata,  // Is this the right approach?
      type: 'text',
      field: "location"
    },
    {
      label: 'Size',
      model: metadata,  // Is this the right approach?
      type: 'number',
      field: "size"
    },
    // Plus approximately 50 more properties...
  ];
};

const controls = buildControls(file.value.metadata);  // Data is already unpacked here
</script>

<template>
  <div v-for="item in controls">
    <v-text-field v-model="item.model[item.field]" :label="item.label" :type="item.type" />
  </div>
</template>

Answer 4

To maintain data reactivity, utilize the computed property in your code like so:

<script setup lang="ts">
interface FileMetadata {
  owner: string,
  location: string,
  size: number,
  // Plus approximately 50 more properties...
}

interface File {
  fileName: string,
  metadata: FileMetadata
}

const file = defineModel<File>({ required: true });

const buildControls = (metadata: FileMetadata) => {
  return [
    {
      label: 'Owner',
      model: metadata,  // Is this the right approach?
      type: 'text',
      field: "owner"
    },
    {
      label: 'Location',
      model: metadata,  // Is this the right approach?
      type: 'text',
      field: "location"
    },
    {
      label: 'Size',
      model: metadata,  // Is this the right approach?
      type: 'number',
      field: "size"
    },
    // Plus approximately 50 more properties...
  ];
};

const controls = buildControls(file.value.metadata);  // Data is already unpacked here
</script>

<template>
  <div v-for="item in controls">
    <v-text-field v-model="item.model[item.field]" :label="item.label" :type="item.type" />
  </div>
</template>

Tips for maintaining data reactivity while transmitting it to a function

Answer №1

Answer №2

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