I'm writing a BlackBerry application which loads XML from a web server and generates objects based on the XML tags. These generated objects all implement the same interface, and are cast to this interface before use.
I've recently implemented menu items in the Messages app which, when selected, launches my app and pushes a screen. This screen is expected to get XML from the server and create objects like normal - and it works, provided it's not called from the menu item.
When called from the menu item, I receive a ClassCastException for only one type of object on the page. Similar objects are cast fine, and this object is cast fine when it's not being instantiated from the menu item class.
Here's where it gets interesting: In the debugger, when Class.forName is run on the XML tag normally, I can highlight the resulting Class object to see
Class my.package.location.ClassName$MyAppName
When I call it from the menu item and get a class cast exception, the Class object appears as
Class my.package.location.ClassName$XMLReflectionTest
I suppose this is why the cast fails, even though both seem to refer to my object.
XMLReflectionTest is not a class or subclass in my project, but Google only returns two search results, neither of which are even somewhat related.
It works fine everywhere else, and even for different classes using the same method! Why would calling Class.forName using the same class string return two "different" classes, based on where it's called from?
I've looked into ClassLoaders, which I could possibly be the issue, but then why would the issue only occur for one class, and not all of them?
Related
I am trying to call a method of a class that I only know by name as a String. Now therefore I would need a ClassMirror of that class that allowes me to instantiate an instance. However, creating ClassMirrors seems to be only possible by entering a type using reflectClass(Type) or by passing an already existing instance of that class into reflect(dynamic). So these aren`t helping if I only have a String.
In Java you can do this pretty easily, by calling Class.forName(String). Then you would get a Constructor instance, make it accessibly and call it.
Does anyone know if this is even possible in dart? What seems weird is that once you have a ClassMirror you can access fields and methods by passing symbols, which can be created by Strings.
You can put a specific list of strings to map to a specific list of closures to create a new object with specific parameters.
But you can't get a reflection without using dart:mirrors, which is being deprecated, and also had a negative impact on tree shaking to get the payload size down.
In general, you're invited to look at the package:reflectable to achieve most of what you'd want out of dart:mirrors, using source-to-source builders.
I've been playing around with a button in my storyboard, and had a hard time getting a border around it, until I found a page where it showed how to add a User Defined Runtime Attribute. I was able to make the button look as I wanted, but I wanted to know if there was a way for me to view the list of available attributes for a particular Object.
Clicking the "+" to add a new attribute doesn't provide any kind of auto-complete to show the available ones, and looking through my project code doesn't seem to reveal anything either, not surprisingly. Is there somewhere I can find all of the available attributes for all/any Objects in Xcode? Searches here on SO and in general have not shown any useful results so far.
You can achieve the same thing from code, so just check the properties of UIButton (which is available in the documentation and with autocomplete) and you're good.
You also have to make sure you are checking the properties on an UIButton instance and not the class properties.
User defined runtime attribute is a list of key paths that NIB loading subsystem uses through unarchived process. After initialisation message -setValue:forKeyPath: will be send to your unarchiving object for each key path from this list. So available attributes are not more than set union of all methods with selector sort of -setAttribute: and ivars with "_attribute" or "attribute" name.
All that public attributes you may find at public headers or documentation.
There's also possible to set private attributes, but it's not good practice. For instance, you may find all ivars by breakpoint execution inside any method and look inside "self".
I cant get my head around this. I was looking at the lynda.com ActionScript 3.0 in Flash Professional CS5 Essential Training. I understand all the other stuff, but this guy places a skater on the stage he has this code on the first frame on the main timeline:
import flash.display.MovieClip;
import flash.events.MouseEvent;
var boarder:MovieClip = boarder_mc;
boarder.stop();
boarder.x = 0;
boarder.y = 0;
boarder.addEventListener(MouseEvent.CLICK, clickedBoarder);
function clickedBoarder(evt:MouseEvent):void
{
boarder.gotoAndPlay(2);
}
function restart():void
{
boarder_mc.gotoAndStop(1);
boarder_mc.x = 0;
}
then on the skater he has a Display Object Container (Movie Clip) in it he has a Display Object a bitmap image of a skater and then an animation on the timeline in the skater where at the end the skater falls. On that last frame he has:
stop();
parent.restart();
He explains that this may not work and it doesnt he gets an error:
1061: Call to a possibly undefined method restart through a reference with static type flash.display:DisplayObjectContainer.
He explains that it knows there is a stop() function on the main timeline, and that it knows there is a restart function on the main timeline, but the datatype is different. He also says that the parent is the main timeline.
He says that we need to put Object(parent).restart();
My question is of what datatype and what is the main timeline (Movieclip, DisplayObject, Display Object Container)?
Why would it be a different datatype?
Thanks
The main timeline is a MovieClip, or if you have a DocumentClass, then probably a custom type that at least extends MovieClip.
However when you ask for "parent" of your skater MovieClip, you are really using the parent property that MovieClip inherits from DisplayObject (ActionScript Docs Here). This property returns the parent as type DisplayObjectContainer, regardless of the type that it actually is. Since it is the parent of a DisplayObject, it doesn't matter type it is it has to extend DisplayObjectContainer, so this is how it is returned.
So when you compile your ActionScript, the compiler looks at "parent" and sees it as type DisplayObjectContainer, looks at its definition of DisplayObjectContainer and errors because DisplayObjectContainer doesn't have a function called "restart".
What you said about the "stop" function is not really correct, since you are not calling stop on the main timeline, your are calling stop on the Skater's timeline. If you wanted to call stop on the main timeline you would need to call parent.stop(), and this would give you the same error, since DisplayObjectContainer doesn't have a method called stop.
These are both compiler errors, and are caused because the compiler is following a set of rules, and it can't make assumptions about what might actually happen when your program is running. It just knows that when you call parent.restart() it might receive a DisplayObjectContainer that won't have the method restart on it, and a run-time error will occur.
Now, by casting parent as type object, you are effectively telling that compiler that this thing can have any method or property on it, since Object is a dynamic class. So the compiler will now assume that you as the developer know that the method "restart" will exists on the "Object" that is given to that bit of code, and therefor will not error any more.
Thank you very much for you reply. This is really confusing. I thought that DisplayObjectContainer is a subclass of Display Object and it extends it? I know that Display Object Container is a Display Object and it can contain other Display objects and Display Object Containers. So the way I understand it, the maintimeline is a movieclip and therefore a DisplayObejctContainer, which can contain other Display objects (that you create in you application) and that is why parent returns Display Object Container, but that it is also a abstract class which means that it cannot have methods such as .restart and goToAndPlay() because it cannot actually be instantiated. However if its a MovieClip as you say then it can..... I dont get it.Does it mean that it is an abstract Class?
I am using Adobe Flash Pro CC, AS3 & scaleform.
I create an instance of an object which contains AS Linkage and a use class definition.
Regardless I can visually identify the object is loaded, the constructor class of this object never gets called.
I tried re-creating the object in the scene, renaming, etc... but it still produces the same error.
When running the GfxMediaPlayer, I can see an 1009 error is displayed; a common mistake when the AS Linkage is missing.
Is there any other option for this kind of objects that is restricting how it gets instantiated?
My scene contains several objects that use similar layout and scaleform.clik libraries, but they work as expected an they do get instantiated.
I also have tested this on Flash CS6 with same results, any help appreciated.
I found that the library path for the object was missing. The strange thing, is that same path was used by the rest of the objects that were working fine, no idea how they would be working.
I've written a small COM Server in Delphi 2010 that acts as a plug-in into a retail application. The retail application looks for a "discover" interface which registers any number of additional interfaces calling TAutoObjectFactory.Create for each one. This is working just fine--all the plug-in interfaces function as designed.
But now I'd like to call a public method of one interface from another interface so I don't have to duplicate code. Seems simple enough, just call ComClassManager.ForEachFactory looking for the ClassID of the interface I need to use. Got that working, too!
But now that I found the class, I'm stumped by a seemingly trivial final step: how to use or cast the class (or class reference?) I've located to actually call one of its methods.
In the "FactoryProc" I've sent to ForEachFactory, I assume the ComClass property of TComObjectFactory is what I'm after, but it's of type TClass, a class reference to the actual class object to which it points (at least I hope I'm understanding this correctly). I'm a little fuzzy on class references and my attempts to cast or otherwise de-reference this property has resulted in access violations or compiler errors.
Any suggestions?
You're right in your comment, ComClassManager deals with classes, not instances. What you need is (your application-local implementation of) running object table (or something similar), so plugin instances can interact with each other.
How to actually implement it depends on what you really need, e.g. call methods on all running instances, or only on instances of specific classes.