# 路由元信息

我们称 `routes` 配置中的每个路由对象为一个**路由记录**。路由记录可以是嵌套的，因此，当一个路由匹配成功后，他可能匹配多个路由记录，例如，下面的路由配置，`/foo/bar` 这个 URL 将会匹配父路由记录以及子路由记录：

```javascript
const router = new VueRouter({
  routes: [
    {
      path: '/foo',
      component: Foo,
      children: [
        {
          path: 'bar',
          component: Bar,
          // a meta field
          meta: { requiresAuth: true }
        }
      ]
    }
  ]
})
```

一个路由匹配到的所有路由记录会暴露为 `$route` 对象 (还有在导航守卫中的路由对象) 的 `$route.matched` 数组。因此，我们需要遍历 `$route.matched` 来检查路由记录中的 `meta` 字段。

下面例子展示在全局导航守卫中检查元字段：

```javascript
router.beforeEach((to, from, next) => {
  if (to.matched.some(record => record.meta.requiresAuth)) {
    // this route requires auth, check if logged in
    // if not, redirect to login page.
    if (!auth.loggedIn()) {
      next({
        path: '/login',
        query: { redirect: to.fullPath }
      })
    } else {
      next()
    }
  } else {
    next() // 确保一定要调用 next()
  }
})
```


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