How to use computed for object attribute?

Question

I want to get an attribute from an object to be computed, but as far as I'm aware, this is not supported.

I have tried using something like objects.atributes:{ /*codes */ } but got errors.

I want to achieve something like this:

<template>
    <div class="form">
        <form>
            <div class="form-group">
                <label>First Name : </label>
                <input type="text"  v-model="firstName" name="firstname" class="form-control">
            </div>
            <div class="form-group">
                <label>Last Name : </label>
                <input type="text"  v-model="lastName" name="lastname" class="form-control">
            </div>
            <div class="card text-center">
                Full name is: {{ formdata.fullname }}
            </div>

        </form>
    </div>
</template>

<script>
export default {
  data(){
    return {
      firstName:'',
      lastName:'',
      formdata:{
        computed:{
          fullname:{
            get:function(){
              return this.firstName + ' ' + this.lastName
            }
          }
        }
      },
    }
  },
  /*    I have tried this too, and got syntax error
  computed:{
    formdata.fullname{
      get:function(){
        return this.firstName + ' ' + this.lastName
      }
    }
  }
  */
}
</script>

I expected the full name to show up, but it didn't.

Answer 1

Computed properties are defined outside of data object. Do it like this:

export default {
    data() {
        return {
            firstName:'',
            lastName:'',
        }
    },
    computed: {
        fullname: function() {
            return this.firstName + ' ' + this.lastName;
        }
    }
}

<div class="card text-center">
    Full name is: {{ fullname }}
</div>