[Vuejs]-Dynamic v-model can't show the value?

Hi is your syntax correct? v-for should look like this <li v-for="(item, index) in design.components">

according to the documentation

https://v2.vuejs.org/v2/guide/list.html

also you have typo in your Vue {field:'c} it should be {field:'c'}

edit:
here is https://jsfiddle.net/v4oxzft7/