Re: JsInterop consuming JS with a attributes

Use an interface rather than a class.

See the note about castability in the javadoc: https://javadoc.io/doc/com.google.jsinterop/jsinterop-annotations/latest/jsinterop/annotations/JsType.html

Rule of thumb is: use a class only if it maps to a "constructor" in JS, i.e. something you'll either create an instance of, or use in an "instanceof" check; for everything else (generally something you get from another API or "receive" in a callback), use an interface.

In this case, I think you could also use name="Object".

On Monday, January 13, 2025 at 7:47:28 AM UTC+1 ma...@craig-mitchell.com wrote:

Overlay types do work, and make it a little better:

public class CrazyGamesUser extends JavaScriptObject {
  protected CrazyGamesUser() {}
  public final native String getUserName() /*-{ return this.username; }-*/;
  public final native String getProfilePictureUrl() /*-{ return this.profilePictureUrl; }-*/;
}

However, it would be great if JsInterop just worked, so I could just do:

@JsType(isNative = true, namespace = JsPackage.GLOBAL)
public static class CrazyGamesUser {
  public String username;
  public String profilePictureUrl;
}

Maybe I'm missing something?

On Monday, 13 January 2025 at 4:02:40 pm UTC+11 Craig Mitchell wrote:

I'm calling some existing JS that returns a JS Object which I've implemented in JsInterop:

@JsType(isNative = true, namespace = "window.CrazyGames.SDK")
public static class JsUser {
    public native Promise<CrazyGamesUser> getUser();
}

I can happily call it:

sdk.user.getUser()
  .then(user -> {
    // Do something with the user
    return null;
  })
  .catch_(error -> {
    return null;
  });

This issue is I'm struggling to work out how to define the return object "CrazyGamesUser".  The actual JS object is just this:

{
    "username": "SingingCheese.TLNU",
    "profilePictureUrl": "https://images.crazygames.com/userportal/avatars/4.png"
}

If I define it like this:

@JsType(isNative = true, namespace = JsPackage.GLOBAL)
public static class CrazyGamesUser {
  public String username;
  public String profilePictureUrl;
}

I get a java.lang.ClassCastException.

So if I set the name to "?":

@JsType(isNative = true, name = "?", namespace = JsPackage.GLOBAL)
public static class CrazyGamesUser {
  public String username;
  public String profilePictureUrl;
}

Then I get a compile error:

'?' can only be used as a name for native interfaces in the global namespace.

But if I make it an interface, I can't have the member variables.

If I do remove the member variables, it does work, and I can access them via some JSNI:

public static native String getUsername(CrazyGamesUser instance) /*-{
  return instance.username;
}-*/;

But that's really ugly.  What's the correct approach here?

Thanks.

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