Why the value of input file missing when I input t

2019-07-15 08:15发布

站内问答 / JavaScript
1081 1 6

I have two component

My first component (parent component) like this : 

<template>
    <div>
        ...
            <form-input id="name" name="name" v-model="name">Name</form-input>
            <form-input id="birth-date" name="birth_date" type="date" v-model="birthDate">Date of Birth</form-input>
            <form-input id="avatar" name="avatar" type="file" v-on:triggerChange="onFileChange($event)">Avatar</form-input>
            <form-input id="mobile-number" name="mobile_number" type="number" v-model="mobileNumber">Mobile Number</form-input>
        ...
    </div>
</template>
<script>
    export default {
        data() {
            return {
                name: null,
                birthDate:  null,
                mobileNumber: null
            }
        },
        methods: {
            onFileChange(e) {
                let self = this
                this.validate(e.target.files[0])
                .then(function(res) {
                    let files = e.target.files,
                    reader = new FileReader()
                    // if any values
                    if (files.length) {
                        self.removeErrorMessageUpload()
                        self.files = files[0]
                        reader.onload = (e) => {
                            self.updateProfileAvatar(e.target.result)
                        }
                        reader.readAsDataURL(files[0])
                    }
                })
                .catch(function() {
                    // do something in the case where the image is not valid
                    self.displayErrorMessageUpload()
                })
            },
            validate(image) {
                let self = this
                return new Promise(function(resolve, reject) {
                    // validation file type
                    if (!self.allowableTypes.includes(image.name.split(".").pop().toLowerCase())) {
                        reject()
                    }
                    // validation file size
                    if (image.size > self.maximumSize) {
                        reject()
                    }
                    // validation image resolution
                    let img = new Image()
                    img.src = window.URL.createObjectURL(image)
                    img.onload = function() {
                        let width = img.naturalWidth,
                            height = img.naturalHeight

                        window.URL.revokeObjectURL(img.src)

                        if (width != 100 && height != 100) {
                            reject()
                        } 
                        else {
                            resolve()
                        }
                    }
                })         
            },
        }
    }
</script>

From the parent component, it will call child component (form input component)

My child component are input type text, input type date, input type file and input type number. I combine all of them into 1 component

The child component like this :

<template>
    <div class="form-group">
        <label :for="id" class="col-sm-3 control-label"><slot></slot></label>
        <div class="col-sm-9">
            <input :type="type" :name="name" :id="id" class="form-control" :value="value" v-on:change="applySelected($event)" @input="$emit('input', $event.target.value)">
        </div>
    </div>
</template>

<script>
    export default {
        name: "form-input",
        props: {
            'id': String,
            'name': String,
            'isRequired': {
                type: Boolean,
                default: true
            },
            'type': {
                type: String,
                default() {
                    if(this.type == 'number')
                        return 'number'
                    return 'text'
                }
            },
            'value': {
                type: [String, Number]
            }
        },
        methods: {
            applySelected(e) {
                this.$emit('triggerChange', e)
            }
        }
    }
</script>

Because I merge into 1 komponent, I get a new problem

If I input the input type file, the value of file will show in the input type file

But if I input in the input type text, the value of input type file missing

Why the value of input type file missing?

Demo:

Vue.component('form-input', {
  template: "#form-input-tpl",
  name: "form-input",
  props: {
    'id': String,
    'name': String,
    'isRequired': {type: Boolean, default: true},
    'type': { type: String, default () {if (this.type == 'number') {return 'number'} else {return 'text'}}},
    'value': { type: [String, Number] }
  },
  methods: {
    applySelected(e) { this.$emit('triggerChange', e) }
  }
});

new Vue({
  el: '#app',
  data: {
    name: null,
    birthDate: null,
    mobileNumber: null
  },
  methods: {
    onFileChange(e) {
      // ...
    }
  }
})
<script src="https://unpkg.com/vue"></script>

<template id="form-input-tpl">
    <div class="form-group">
        <label :for="id" class="col-sm-3 control-label"><slot></slot></label>
        <div class="col-sm-9">
            <input :type="type" :name="name" :id="id" class="form-control" :value="value" v-on:change="applySelected($event)" @input="$emit('input', $event.target.value)">
        </div>
    </div>
</template>

<div id="app">
  <h3>Select a file, then type a name. The file will be reset.</h3>
  <div>
    <form-input id="name" name="name" v-model="name">Name</form-input>
    <form-input id="birth-date" name="birth_date" type="date" v-model="birthDate">Date of Birth</form-input>
    <form-input id="avatar" name="avatar" type="file" v-on:triggerChange="onFileChange($event)">Avatar</form-input>
    <form-input id="mobile-number" name="mobile_number" type="number" v-model="mobileNumber">Mobile Number</form-input>
  </div>
</div>

1条回答
聊天终结者
2楼-- · 2019-07-15 08:37

So the problem is:

After you have chosen a file in the <form-input type="file">, if you type something in the <form-input type="type">, the <form-input type="file"> erases. Why is that?

This happens because when you edit <form-input type="text">, Vue will "repaints" the components.

And when it repaints the <form-input type="file">, it will go back to "Nothing selected" because it is a new <input type="file">.


Solution: Keeping the files' values

As Kaiido points in the comments, in latest versions of browsers, you can set the files of a <input type="file"> in a standard way.

So this is what the code below does. It watches for the value property (that comes when the parent uses v-model and sets its value to the .files property of the <input type="file">.

We have to use two <input> (with v-if/v-else) because when it is a <input type="file">, the :value property can be set, the event handler should be different (@change="$emit('input', $event.target.files)") and we want to keep a ref so we can set the files.

Full working demo below.

Vue.component('form-input', {
  template: "#form-input-tpl",
  name: "form-input",
  props: {
    'id': String,
    'name': String,
    'isRequired': {type: Boolean, default: true},
    'type': {type: String, default: 'text'},
    'value': {type: [String, Number, FileList, DataTransfer]}
  },
  mounted() {
    // set files upon creation or update if parent's value changes
    this.$watch('value', () => {
      if (this.type === "file") { this.$refs.inputFile.files = this.value; }
    }, { immediate: true });
  }
});

new Vue({
  el: '#app',
  data: {
    name: null,
    birthDate: null,
    mobileNumber: null,
    files: null
  }
})
<script src="https://unpkg.com/vue"></script>

<template id="form-input-tpl">
    <div class="form-group">
        <label :for="id" class="col-sm-3 control-label"><slot></slot></label>
        <div class="col-sm-9">
           <input v-if="type !== 'file'" :type="type" :name="name" :id="id" class="form-control" :value="value" @input="$emit('input', $event.target.value)">
            
           <input v-else :type="type" :name="name" :id="id" class="form-control" @change="$emit('input', $event.target.files)" ref="inputFile">
        </div>
    </div>
</template>

<div id="app">
  <div>
    <form-input id="name" name="name" v-model="name">Name</form-input>
    <form-input id="birth-date" name="birth_date" type="date" v-model="birthDate">Date of Birth</form-input>
    <form-input id="avatar" name="avatar" type="file" v-model="files">Avatar</form-input>
    <form-input id="mobile-number" name="mobile_number" type="number" v-model="mobileNumber">Mobile Number</form-input>
  </div>
</div>

Using your file-change event and validate function:

Vue.component('form-input', {
  template: "#form-input-tpl",
  name: "form-input",
  props: {
    'id': String,
    'name': String,
    'isRequired': {type: Boolean, default: true},
    'type': {type: String, default: 'text'},
    'value': {type: [String, Number, FileList, DataTransfer]}
  },
  mounted() {
    // set files upon creation or update if parent's value changes
    this.$watch('value', () => {
      if (this.type === "file") { this.$refs.inputFile.files = this.value; }
    }, { immediate: true });
  }
});

new Vue({
  el: '#app',
  data: {
    name: null,
    birthDate: null,
    mobileNumber: null,
    filesVModel: null,
    allowableTypes: ['jpg', 'jpeg', 'png'],
    maximumSize: 1000,
    files: null
  },
  methods: {
    onFileChange(e) {
      console.log('onfilechange!');
      let self = this
      this.validate(e.target.files[0])
        .then(function(res) {
          let files = e.target.files,
            reader = new FileReader()
          // if any values
          if (files.length) {
            self.removeErrorMessageUpload()
            self.files = files[0]
            reader.onload = (e) => {
              self.updateProfileAvatar(e.target.result)
            }
            reader.readAsDataURL(files[0])
          }
        })
        .catch(function(err) {
          // do something in the case where the image is not valid
          self.displayErrorMessageUpload(err)
        })
    },
    validate(image) {
      let self = this
      return new Promise(function(resolve, reject) {
        // validation file type
        if (!self.allowableTypes.includes(image.name.split(".").pop().toLowerCase())) {
          reject("Type " + image.name.split(".").pop().toLowerCase() + " is not allowed.")
        }
        // validation file size
        if (image.size > self.maximumSize) {
          reject("Image size " + image.size + " is larger than allowed " + self.maximumSize + ".")
        }
        // validation image resolution
        let img = new Image()
        img.src = window.URL.createObjectURL(image)
        img.onload = function() {
          let width = img.naturalWidth,
            height = img.naturalHeight

          window.URL.revokeObjectURL(img.src)

          if (width != 100  && height != 100) {
            reject("Width and height are " + width + " and " + height + " and not both 100")
          } else {
            resolve()
          }
        }
      })
    },
    displayErrorMessageUpload(msg) {
      console.log('displayErrorMessageUpload', msg);
    },
    removeErrorMessageUpload() {
      console.log('removeErrorMessageUpload');
    },
    updateProfileAvatar(result) {
      console.log('updateProfileAvatar', result);
    }
  }
})
<script src="https://unpkg.com/vue"></script>

<template id="form-input-tpl">
    <div class="form-group">
        <label :for="id" class="col-sm-3 control-label"><slot></slot></label>
        <div class="col-sm-9">
           <input v-if="type !== 'file'" :type="type" :name="name" :id="id" class="form-control" :value="value" @input="$emit('input', $event.target.value)">
            
           <input v-else :type="type" :name="name" :id="id" class="form-control" @change="$emit('input', $event.target.files)" ref="inputFile" v-on:change="$emit('file-change', $event)">
        </div>
    </div>
</template>

<div id="app">
  <div>
    <form-input id="name" name="name" v-model="name">Name</form-input>
    <form-input id="birth-date" name="birth_date" type="date" v-model="birthDate">Date of Birth</form-input>
    <form-input id="avatar" name="avatar" type="file" v-model="filesVModel" @file-change="onFileChange">Avatar</form-input>
    <form-input id="mobile-number" name="mobile_number" type="number" v-model="mobileNumber">Mobile Number</form-input>
  </div>
</div>

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