Vue component, how to access properties vs data

So I've started to work with Vue Js and I don't understand how the accessing of data and propeties works. I've got a very basic Vue component that fires a method when you press enter. Basically I want to send a post request with A: the value of the textfield (got that to work) and B: the value of a property I'm giving in the html tag (parentCategory) . I can't seem to access the parentCategory property. I know you would access it in the template like you would any data but when I console.log the value of the parentCategory It's undefined.

<script>
    export default
    {
        data() {
            return {
                category: {
                    name: '',
                    category_id: ''
                },
            showfield: false
            }
        },
        props() {
            ['parentCategory']
        },
        methods: {
            createCategory() {
                
                console.log(this.parentCategory)
                this.category.category_id = this.parentCategory
                console.log(this.category.category_id)
                this.$http.post('/categories', this.category).then((response) => {
                  console.log('received')
                }, (response) => {
                  console.log('failed to store')
                  //Remember that this might not fire if the backend failed.
                });
            }
        }
    }
</script>

What am I missing here? Is there a different way to access properties in component methods?