parent.vue
<Child v-for="(it, idx) of something" @someevent="arg => somemethod(arg, idx)"/>
child.vue
<button @click="$emit('someevent', arg)">Magic!</button>
parent.vue
<Child v-for="(it, idx) of something" @someevent="arg => somemethod(arg, idx)"/>
child.vue
<button @click="$emit('someevent', arg)">Magic!</button>