Scala模板中的if语句播放框架

Question

hey guys am trying to send a value for user if he is logged in and in not i execute an if statement in a home page scala template

 User loggeduser = User.find.query().where().eq("token", 
 session("connected")).findOne();
 return ok(main.render(loggeduser));

in scala home page template am trying something like this

@(user: User)
@if(user.fname==null){ i even tried @if(user.isEmpty)

and tried to keep fname outside yet the same error for a NULL POINTER EXEPTION then show some login form links

}else(user!=null){
<a class="dropdown-toggle" data-toggle="dropdown" id="signHover">@user.fname</a>

}

please if have any suggestion guide me throw the process

reference : https://www.playframework.com/documentation/2.6.x/JavaTemplates

Answer 1

Assuming User is null if there's no user, shouldn't you have

@(user: User)
@if(user!=null){ 
  // do stuff
} else {
  // do stuff for no user
}

Answer 2

In scala homepage template am trying something like this

@(user: User)
@if(user.fname==null){ i even tried @if(user.isEmpty)

Answer 3

If user can be null, use Option[User] instead of User. Inside a template you can use fold in order to handle Option.

In Scala is a bad practice to use null. If a variable can be null, use Option instead, let it be known that a variable can be null, expressivity over all.

@(userOpt:Option[User])

<div>SOME HTML</div>

@userOpt.fold {
    <div>USER ISN'T LOGGED</div>
} { user =>
    <div>USER IS LOGGED! @user</div>
}

<div>SOME HTML</div>