You can easily replace myClass.isInstance(myInstance) by myClass.equals(myInstance.getClass())
Michel. On Saturday, February 17, 2007 7:22:36 PM UTC+1, Ian Petersen wrote: > > > you're forgetting that you can use instanceof ONLY if you have a class > > that you KNOW, at write-time. The Class.instanceOf idea (or the GWT > > replacement for it) has no such restriction. You can e.g. make a > > method that takes a widget and a list of class names and returns if > > the widget is one of those. You can make this 'generic' (e.g: one > > method that works for any list of class names and any widget). With > > the instanceof keyword, you can't do this; you'd have to make one > > method for each list of classes you do have. > > I don't want this to descend into a flamewar, so please understand I'm > not trying to criticize anyone or anything--I just want to better > understand what you've written. > > I already know that instanceof requires write-time knowledge of the > class and that, as implemented in a full implementation of the Java > library, java.lang.Class.isInstance() does _not_ require write-time > knowledge of the class on which you're calling isInstance(). > > What I'm questioning is the benefit of using isInstance() in a GWT > client-side application. It appears that the JRE emulation library > for GWT does not include any instance methods for java.lang.Class, > which makes instances of Class nearly useless within GWT except as > tokens for use as keys in maps, or similar. > > You suggested using a class literal as follows: > > boolean b = SomeClassOrOther.class.isInstance(widget); > > I figured, in response, that the GWT compiler must be able to figure > out that this is supposed to be equivalent to: > > boolean b = widget instanceof SomeClassOrOther; > > because we already know the compiler has special handling for class > literals like Foo.class. (This is how the compiler handles > GWT.create(Foo.class)--it knows that Foo.class is special.) > > So, I'm assuming that you know that the GWT compiler can handle > Foo.class.isInstance(bar). It's already been established by Mike that > > Class foo = Foo.class; > boolean b = foo.isInstance(bar); > > won't work because foo doesn't have any instance methods (besides > those defined on Object). > > So, since you can't store Foo.class in a variable (or pass it as a > parameter) and _then_ call isInstance() on it, I don't see the benefit > of (Foo.class.isInstance(bar)) over (bar instanceof Foo) especially > since you pointed out that, within GWT, isInstance() won't return true > for arguments that are instances of subclasses of the method's > subject. > > Ian > > -- > Tired of pop-ups, security holes, and spyware? > Try Firefox: http://www.getfirefox.com > > -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/XBcYplfi4LQJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
