Javascript vtextfield的规则找不到数据中声明的元素

我正在使用Vue3和Vuetify，当为确认密码字段的v-textfield制定规则时，我遇到了这个错误:

I tried to compare the values of the password field and the one of the confirm password field, both associeted to the v-textfield with the v-model, but in the confirm password rule the variable of the password results undefined.
Here's the source.

Data whit rules and variables:

data: () => ({
  // Credentials
  username: '',
  password: '',
  confirmPassword: '',

  passwordRules: [
    (value) => {
      if (value?.trim().length > 0) return true
      else return 'Password is required.'
    },
  ],
  confirmPasswordRules: [
    (value) => {
      if (value?.trim().length > 0) {
        // TODO: ERROR (this.password is undefined)
        if(value === this.password) {
          return true
        }
        else return 'Passwords do not match.'
      }
      else return 'Confirm password is required.'
    },
  ],
}),

当我在v-textfield中写入字符时，错误总是出现，因为它在规则中:

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'password')
    at confirmPasswordRules

谢谢！