How to embed a variable in a class that changes by condition?

Question

Vue.js

The code

<a href="#" :class="{'list-group-item-'+list.tag: list.approved}">{{list.name}}</a>

In Approved true/false
Swears
invalid expression: Unexpected token + in
How it is correct to register all this?
Tasks:
Changing a class by condition
Embedding a variable in a class

Answer 1

Take object key in []