GAE Go —如何将GetMulti与不存在的实体密钥一起使用？

问题描述：

I've found myself needing to do a GetMulti operation with an array of keys for which some entities exist, but some do not.

My current code, below, returns an error (datastore: no such entity).

err := datastore.GetMulti(c, keys, infos)

So how can I do this? I'd use a "get or insert" method, but there isn't one.

我发现自己需要对键数组进行GetMulti code>操作 p>

下面的我当前的代码返回错误（数据存储区：没有这样的实体 code>）。 p> \ n

err：= datastore.GetMulti（c，键，信息） code> p>

那我该怎么做呢？我会使用“获取或插入”方法，但是没有。 p> div>

答

GetMulti can return a appengine.MultiError in this case. Loop through that and look for datastore.ErrNoSuchEntity. For example:

if err := datastore.GetMulti(c, keys, dst); err != nil {
    if me, ok := err.(appengine.MultiError); ok {
        for i, merr := range me {
            if merr == datastore.ErrNoSuchEntity {
                // keys[i] is missing
            }
        }
    } else {
        return err
    }
}

答

I know this topic is up for more than a few days, but I like to post an alternative, using type switch.

if err := datastore.GetMulti(c, keys, dst); err != nil {
  switch errt := err.(type) {
  case appengine.MultiError:
    for ix, e := range errt {
      if e == datastore.ErrNoSuchEntity {
        // keys[ix] not found
      } else if e != nil {
        // keys[ix] have error "e"
      }
    }
  default:
    // datastore returned an error that is not a multi-error
  }
}

GAE Go —如何将GetMulti与不存在的实体密钥一起使用？

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