这个composable指向包装了你自己的自定义组件（你想与之沟通）的QForm。

Syntax

import { useFormChild } from 'quasar'

setup () {
  // function validate () { ... }
  // function resetValidation () { ... }

  useFormChild({
    validate, // Function; Can be async;
              // Should return a Boolean (or a Promise resolving to a Boolean)
    resetValidation,    // Optional function which resets validation
    requiresQForm: true // should it error out if no parent QForm is found?
  })
}