v-for错误提示[vue-language-server] Elements in iteration expect to have 'v-bind:key' directives. Rend...

Vue 2.2.0+的版本里，当在组件中使用v-for时，key是必须设置的:

注意上面key值不要用对象或是数组作为key，用string或number作为key，否则报错：[Vue warn] Avoid using non-primitive value as key, use string/number value instead.