Using a generic type for the generic type of SpiceRequest about robospice

[jeffdgr8]

I found a workaround (documented in StackOverflow post), but this may pop up as a common issue for people with the constructor formatted the way it is. In my case, the object returned by my network service is a Map with various Objects (Strings, Integers, ArrayLists, etc.) from an XML-RPC call and so I need to use the generic class type Map<String, ? extends Object> for the result type in SpiceRequest.

[stephanenicolas]

Hi @jeffdgr8,

this problem is not really related to RoboSpice itself but to a limitation of the Java syntax : there is no litteral that you can use to get the class/type of a parametrized generic type in Java.

If you want to do something like

public class ListTweetRequest extends SpiceRequest<List<Tweet>> {

   public ListTweetRequest(Object cacheKey ) {
       super( <Here is the problem>, cacheKey );
   }
}

then you can't pass the class List<Tweet>.class to you parent constructor. That's really a Java limitation as generics are realized using type erasure and List<Tweet>.class has no real meaning in Java.

The best and cleanest work around is to use an intermediate type like :

public class ListTweet extends List<Tweet> {
}

public class ListTweetRequest extends SpiceRequest<ListTweet> {

   public ListTweetRequest(Object cacheKey ) {
       super( ListTweet.class, cacheKey );
   }
}

This has the advantage to provide you with a real type that you can pass to the SpiceRequest's constructor. But beware of obfuscation. In thoses cases, proguard will try to remove the ListTweet class, you have to explicitly preserve it from obfuscation.

[jeffdgr8]

OK, thank you for the info. That is helpful.