对片段真的很困惑
我的电梯视野有问题。问题是，我进行了两次昂贵的远程rest-api 调用 - 我实际上只需要执行一次。
但我不知道如何解决这个问题。
基本上我有一个像这样的 HTML 模板，需要显示用户列表及其计数：
//UserSearchResults.html
Num users: <span class="lift:UserSearchResults.userCount"></span>
User list:
<ul>
<lift:UserSearchResults.userList>
<li><user:userName/></li>
</lift:UserSearchResults.userList>
</ul>
然后我有一个实际的代码片段，用于从rest-api 服务器检索用户列表。但是，请注意，它实际上执行了两次 - 一次用于计算用户数量，一次用于呈现列表。
//UserSearchResults.scala
/** Get list of users from api */
def users: List[User] = {
val url = "http://server/rest-api/user-search";
val result = io.Source.fromURL(url).mkString
//... parse users into List[User] and return it
return entries
}
/** Render user count */
def userCount =
"* *" #> users.length //<-- ONE call
def userList(in: NodeSeq): NodeSeq = {
users.flatMap(user => Helpers.bind("user", in, //<--SECOND call
"userName" -> user.user_name))
}
有没有更好的地方来放置 api 调用？代码片段是否有一个“构造函数”，我可以使用它来缓存用户列表，并在类中的所有函数之间共享它？
任何帮助表示赞赏。
I have a problem with my lift view. The thing is, I am making an expensive remote rest-api call twice - where I should really need to do it only once.
But I can't figure out how to solve this.
Basically I have an HTML template like this, that needs to display the list of users and their count:
//UserSearchResults.html
Num users: <span class="lift:UserSearchResults.userCount"></span>
User list:
<ul>
<lift:UserSearchResults.userList>
<li><user:userName/></li>
</lift:UserSearchResults.userList>
</ul>
And then I have an actual snippet that goes and retrieves the list of users from the rest-api server. However, note that it actually does this TWICE - once to count the number of users, and once to render the list.
//UserSearchResults.scala
/** Get list of users from api */
def users: List[User] = {
val url = "http://server/rest-api/user-search";
val result = io.Source.fromURL(url).mkString
//... parse users into List[User] and return it
return entries
}
/** Render user count */
def userCount =
"* *" #> users.length //<-- ONE call
def userList(in: NodeSeq): NodeSeq = {
users.flatMap(user => Helpers.bind("user", in, //<--SECOND call
"userName" -> user.user_name))
}
Is there a better place to put the api call? Is there like a "constructor" for the snippet, that I can use cache the user list, and to share it across all the functions in the class?
Any help is appreciated.
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如果 UserSearchResults 是一个类（而不是一个对象），那么每个请求都会有一个该类的实例。因此，您所要做的就是将 def 用户更改为惰性 val 用户，然后就可以开始了。
If UserSearchResults is a class (as opposed to an object), then there will be a per-request instance of that class. As such, all you have to do is change your def users to a lazy val users and you should be good to go.
如果您的代码片段扩展了 StatefulSnippet，您只需将列表保存在实例变量中即可。另一种选择是将列表放入 RequestVar 中。然后也可以从其他片段访问它。
If your snippet extends StatefulSnippet, you can just save the list in an instance variable. Another option would be to put the list into a RequestVar. Then it could also be accessed from other snippets.