Passing index with file using dropzone

I am using dropzone in vue js and would like to pass the index with the file to add the file to the corresponding array.

    <div v-for="(lang, key) in $v.model.langs.$each.$iter" :key="key">
          <Dropzone id="bar" ref="bar"  @vdropzone-complete="vfileAdded" :options="options" :destroyDropzone="true" :useCustomSlot="true">
      </Dropzone>
    </div>

here is my method

     vfileAdded(file) {
        console.log(file)
     },

In this case I get file to my method but if I using @vdropzone-complete="vfileAdded(file,key)"
and method

      vfileAdded(file, key) {
        console.log(file)
      },

this I receives key parameter but file is undefined.

How can I pass file with key to my method vfileAdded