I want to extend the FileReference class of Flex to contain a custom property. I want to do this because AS3 doesn't let me pass arguments to functions through event listeners, which makes me feel sad, so I need this property to exist on the event target, so I can access it.
I also want to be able to cast extant FileReference objects to this class without any fuss. I have:
var fr:SmxFR = e.target as SmxFR
and I want that to work; right now it just returns null.
A blank, newly instantiated SmxFR object has the extended property in place, but all of its inherited properties and objects return Error: Error #2037: Functions called in incorrect sequence, or earlier call was unsuccessful.
This is the class I am using, SmxFR.as:
package
{
import flash.net.FileReference;
public class SmxFR extends FileReference
{
public var housenum:String = "";
public function SmxFR()
{
super();
}
}
}
Kept it as straightforward as I could, really. Can someone please help me figure this out? Thanks.
Edit:
Per request, this is the instantiation which results in the aforementioned error in all inherited objects:
var fr:SmxFR = new SmxFR();
I get living handle property from that, and all other (that is, inherited) properties throw Error #2037.
So, maybe what I want to do is going to require overriding FileReferenceList? If the original objects must be instantiated to SxmFR, that's what I'll have to do, since I'm using FRL to allow the user to select multiple files at once. Are you guys sure there is no way to fast from a FileReference to my class?
You can totally pass objects via event listeners, it's just done in a specific way. I'd learn to do it correctly, rather than trying to extend a core library which could cause you problems later if you make a small mistake.
My solution: instead of extending FileReference, extend Event and add your properties to that.
var myEvent:MyExtendedEvent = new MyExtendedEvent();
myEvent.myCustomProperty = myValue;
dispatchEvent(myEvent);
Then in your handler you just write:
function myEventHandler(e:MyExtendedEvent):void {
trace(e.myCustomProperty);
}
Much more painless to go down this road! The added benefit is that if any other Flash Developer anywhere ever looks at your code they're not going to get hit in the face with a non-standard customized FileReference. :)
When e.target is instantiate as FileReference you can't cast it to SmxFR because it's not in the line of inheritance. In the other way you can a SmxFR Object to FileRefernce.
Extending FileReferenceList is not going to be helpful. FileReferenceList.browse() method creates an array of FileReference object when user selects multiple files - that happens internally (may be in its private methods) and you cannot change that behavior and force it to create SxmFR objects instead. Use custom events as Myk suggested.
This article talks about Sound objects, but may be that's applicable to FileReference objects too. May be you cannot reuse them. Post the code where you use the SmxFr class and get the said error.
Related
I'm wondering if there's any reasonable way to get a reference to an object in Flex, and look through everything in every sub object (every property and everything). That is, I want to know if I can completely map all of the data within an object, from another object. I'm aware that this wouldn't work for private (or protected) members, but for anything public, it should be possible, correct?
Use describeType for class instances, and
for (var str:String in obj) { trace (str+":"+obj[str]); }
for simple Objects.
Ok, ObjectUtil.copy is a good technique for copying Objects. But after having a lot of problems using it to copy other classes, I guess it is not the solution I'm after.
How would you approach the copying/cloning of instances of a class that you've defined? Maybe defining a function withing the class to copy it?
It is cool that most variables are passed by reference in flex, but sometimes is annoying not having control over this (sorry, I'm too used to plain C).
Thanks!
UPDATE:
To be more precise, as I can't make the ObjectUtil.copy() work with a custom class is... is there a way to copy, by using serialization, a custom class? Did you use successfully a ByteArray copy with a custom class?
Thanks for all the replies.
If you determine that implementing a clone interface is not the correct approach in your situation, I suggest looking at the ByteArray object. I haven't used it myself, but it appears to give you all the control you should need over individual bytes. You can reading and writing from and to any object.
Senocular does a quick overview of it here.
function clone(source:Object):* {
var copier:ByteArray = new ByteArray();
copier.writeObject(source);
copier.position = 0;
return(copier.readObject());
}
Good luck!
ObjectUtil.copy uses ByteArray internally to create a copy. In order for the copy to be successful, ByteArray requires that the flash player will be aware of you custom class. You do that by registering your class using the global registerClassAlias method.
For example:
//one time globally to the application.
registerClassAlias(getQualifiedClassName(CustomClass), CustomClass);
//then
var c1:CustomClass = new CustomClass();
c1.name = "customClass";
var c2:CustomClass = ObjectUtil.copy(c1);
trace(ObjectUtil.toString(c1))
trace(ObjectUtil.toString(c2))
If you have control over the whole class hierarchy, I recommend implementing a clone() interface in every class. It's tedious, but will pay off as complexity increases.
(Forgive me if the syntax is a bit off, it's been a while)
// define a "cloneable" interface
public interface ICloneable {
function clone() : Object;
}
For every class, implement the method...
public class MyClass1 implements ICloneable {
...
public function clone() : Object {
var copy:MyClass1 = new MyClass1();
// copy member variables... if it is a user-defined object,
// make sure you call its clone() function as well.
return copy;
}
}
To create a copy of the object, simply invoke the clone() function.
var copy:MyClass1 = original.clone();
As a side note, both Java and .NET seem to have adopted the clone methods on their base Object classes. I know of no analogous method for ActionScript's Object class.
Two common idioms:
a clone method
a copy constructor
Both of these let you define what exactly making a copy means--you may want some things copied shallowly and others deeply.
Is there any way to get interface to play along with custom namespace? Example follows.
IHeaderRenderer.as:
public interface IHeaderRenderer{
function set header(value:IHeader):void;
function get header():IHeader;
}
HeaderRenderer.as
import fi.test.internalNamespace;
public class HeaderRenderer implements IHeaderRenderer{
internalNamespace function set header(value:IHeader):void{
// do something
}
internalNamespace function get header():IHeader{
// do something
}
}
This gives you the basic compiler error:
1044: Interface method get header in namespace fi.gridutils.headerrenderers:IHeaderRenderer not implemented by class fi.gridutils.headerrenderers.implementation:HeaderRenderer.
Why is this needed, you might ask. I'm developing a component, where the header accessors should not be directly visible to the components end user (developer), but if the developer wants to create his own Renderer he should know that they are needed. This is because the parent component will use these accessors to give the custom renderer the data it needs to render the header correctly.
Now to my mind there seems to be only three choices:
1) use public access control. This has the setback that the end developer will see accessors, which should not be directly accessed by him. Plus they add unnecessary clutter as they appear in auto-complete.
2) do not use interface. This means the end user has pretty poor options of developing the component further.
3) use the interface, but omit the accessors that use internalNamespace. Now the end developer will not know that he should add also header accessors to his custom headerrenderer class, which ends up in Flash Player giving following error to the developer in runtime:
Cannot create property internalNamespace/::header on fi.gridutils.headerrenderers.implementation.HeaderRenderer.
Sorry for all the blabbing. Any cunning ideas how this kind of situation could be handled?
In ActionScript, the interface methods need to be public. What good is an interface, if you can't guarantee the component using it can access the relevant interface methods?
that said, you can use the exclude metadata to prevent properties from showing up in code hinting.
Something like this:
[Exclude(name="header", kind="property")]
More info
I have a Flex application which references a separate MXML file as a template for a custom component. I create instances of the component dynamically several times in my program, but I need to get a handle that will allow me to modify that instance of the component as desired.
I pass specific information to this component on instantiation using bindable public variables in the component's MXML file. I add it to my main program using addChild().
I want to update the component's progressbar as necessary and I want to remove it from the box to which I addChild'd it.
What's the easiest/best way to get a variable that will give me predictable access to each component so I can easily manipulate the components as necessary? Some research suggests creationComplete, but I decided it was faster to just ask than to go through lots of different experiments and come up blank.
Thanks for all the help. : )
Can you not just keep a list of your components in an array? Presumably you have an object reference when you create them and call addChild() on their parent. Why not just put them in an array at the same time?
var list_of_controls:Array = new Array();
var new_Object:<yourType>;
new_Object = new <yourType>();
parent.addChild(new_Object);
list_of_controls.push(new_Object);
then you can get at them...
var my_Object:<yourType>;
for each (my_Object in list_of_controls)
{
// do something
}
You would have to make sure you dispose of them properly when you re done because the reference in your array would keep them in existence until cleared.
If you decide that you want to use getChildren() instead - which you could - take the time to read the documentation because I think it returns a new array with each call.
I hope that helps.
I'm re-writing an MXML item renderer in pure AS. A problem I can't seem to get past is how to have each item renderer react to a change on a static property on the item renderer class. In the MXML version, I have the following binding set up on the item renderer:
instanceProperty={callInstanceFunction(ItemRenderer.staticProperty)}
What would be the equivalent way of setting this up in AS (using BindingUtils, I assume)?
UPDATE:
So I thought the following wasn't working, but it appears as if Flex is suppressing errors thrown in the instanceFunction, making it appear as if the binding itself is bad.
BindingUtils.bindSetter(instanceFunction, ItemRenderer, "staticProperty");
However, when instanceFunction is called, already initialized variables on the given instance are all null, which was the cause of the errors referenced above. Any ideas why this is?
You have 2 options that I am aware of:
Option 1
You can dig into the code that the flex compiler builds based on your MXML to see how it handles binding to static properties. There is a compiler directive called -keep-generated-actionscript that will cause generated files to stick around. Sleuthing through these can give you an idea what happens. This option will involve instantiating Binding objects and StaticPropertyWatcher objects.
Option 2
There is staticEventDispatcher object that gets added at build time to classes containing static variables see this post http://thecomcor.blogspot.com/2008/07/adobe-flex-undocumented-buildin.html. According to the post, this object only gets added based on the presence of static variables and not getter functions.
Example of Option 2
Say we have a class named MyClassContainingStaticVariable with a static variable named MyStaticVariable and another variable someobject.somearrayproperty that we want to get updated whenever MyStaticVariable changes.
Class(MyClassContainingStaticVariable).staticEventDispatcher.addEventListener(
PropertyChangeEvent.PROPERTY_CHANGE,
function(event:PropertyChangeEvent):void
{
if(event.property == "MyStaticVariable")
{
someobject.somearrayproperty = event.newValue as Array;
}
});
I think you need to respond to the "PropertyChanged" event.
If you're going to do that, use a singleton instead of static. I don't think it will work on a static. (If you have to do it that way at all, there are probably a couple ways you could reapproach this that would be better).
var instance:ItemRenderer = ItemRenderer.getInstance();
BindingUtils.bindProperty(this, "myProperty", instance, "theirProperty");
After fiddling with this for a while, I have concluded that this currently isn't possible in ActionScript, not even with bindSetter. It seems there are some MXML-only features of data bindings judging by the following excerpt from the Adobe docs (though isn't it all compiled to AS code anyways)?
You cannot include functions or array
elements in property chains in a data
binding expression defined by the
bindProperty() or bindSetter() method.
For more information on property
chains, see Working with bindable
property chains.
Source: http://livedocs.adobe.com/flex/3/html/help.html?content=databinding_7.html
You can create a HostProxy class to stand in for the funciton call. Sort of like a HostFunctionProxy class which extends from proxy, and has a getProperty("functionInvokeStringWithParameters") which will invoke the function remotely from the host, and dispatch a "change" event to trigger the binding in typical [Bindable("change")] Proxy class.
You than let the HostProxy class act as the host, and use the property to remotely trigger the function call. Of course, it'd be cooler to have some TypeHelperUtil to allow converting raw string values to serialized type values at runtime for method parameters (splitted by commas usually).
Example:
eg.
var standInHost:Object = new HostFunctionProxy(someModelClassWithMethod, "theMethodToCall(20,11)");
// With BindingUtils.....
// bind host: standInHost
// bind property: "theMethodToCall(20,11)"
Of course, you nee to create such a utlity to help support such functionality beyond the basic Flex prescription. It seems many of such (more advanced) Flex bindings are usually done at compile time, but now you have to create code to do this at runtime in a completely cross-platform Actionscript manner without relying on the Flex framework.