For a while now in my app I've used ObjectUtil.copy to copy array collections. Recently we've been making a lot of changes to the app and its started breaking on any of my copy commands. I originally thought it was due to custom classes in the arrays but ruled that out by testing empty or simple ArrayCollections.
Neither of these will work for me:
var a:ArrayCollection = ObjectUtil.copy(new ArrayCollection());
newWindow.months = ObjectUtil.copy(months) as ArrayCollection;
In the second line, newWindow is just a new canvas I'm going to show with a 'months' property and months is an ArrayCollection with only strings in it.
Inside the .copy() function it breaks on buffer.writeObject(value); and throws this error 'ArgumentError: Error #2004: One of the parameters is invalid.'
Copy source array
newWindow.months = new ArrayCollection(ObjectUtil.copy(months.source) as Array);
Related
I have two ArrayCollection now (a, b) and a is set bindable. I want to reset a with b.
The old code in our project is like:
a = new ArrayCollection();
for (var i:int = 0; i < b.length; i++) {
a.addItem(b.getItemAt(i));
}
Then, I think it may cause a potential memory leak. So I changed it to:
a.removeAll();
for (var i:int = 0; i < b.length; i++) {
a.addItem(b.getItemAt(i));
}
Then I read a topic: Flex optimization tip: ArrayCollection.removeAll() vs. ArrayCollection.source = new Array(). Is this a bug ?
It says removeAll() will cause a performance problem when the data set is large.
So does it means there is a trick off? If the data set is small I should use removeAll, and if the data set is large, I should not use removeAll()?
Another question, I also read a topic about Changing the source of an ArrayCollection.
It says if directly use a = b, "it will kill all the databound controls that are listening to events on the ArrayCollection instance". I don't understand this. I tried a = b, and it works ok (the view that use a as dataprovider updates).
What's the difference between using a=b and a.source = b.source?
I'm new to Flex. Thanks in advance.
ArrayCollection is a wrapper class around Array, and underlying Array can be access using source property
The ArrayCollection class is a wrapper class that exposes an Array as
a collection that can be accessed and manipulated using the methods
and properties of the ICollectionView or IList interfaces. Operations
on a ArrayCollection instance modify the data source; for xample, if
you use the removeItemAt() method on an ArrayCollection, you remove
the item from the underlying Array.
so one should always use Source property of ArrayCollection, if have populated Array
i suggest to declare b as Array not as ArrayCollection and initialize a as
a = new ArrayCollection(b); or
a= new ArrayCollection();// Default constructor ArrayCollection(source:Array=null);
a.source = b; //updates data in Arraycollection
Data Binding means bound controls with datasource(could be any thing like functions, objects, other control, Array, XML, Collection, List etc)
Data binding is the process of tying the data in one object to another
object. It provides a convenient way to pass data between the
different layers of the application. Data binding requires a source
property, a destination property, and a triggering event that
indicates when to copy the data from the source to the destination. An
object dispatches the triggering event when the source property
changes.
Data Binding could be harmful for application with large data because it would creates multiple changes events and both getter and setter executes on change, which need extra proccessing so it would be good practice to shorter scope of a and provide data directly to source as
private function handler_B_DataChange(event:Event)
{
var a:Arraycollection = new ArrayCollection(b);
controlA.dataProvider = a;
//or just
controlB.dataProvider = new ArrayCollection(b);
}
Details of binding could be view on Binding to functions, Objects, and Arrays
Hopes that Helps
I would also try:
a.removeAll();
a.addAll(b.list);
When you declare:
a = new ArrayCollection()
it loses the pointer to the "old" ArrayCollection where it is binded to your application. Thus, that is why when you do "new ArrayCollection" the binding doesn't work anymore. However, in your example, you're not creating a "new ArrayCollection"... you're just replacing the objects in that ArrayCollection with something else... So the binding still works.
If you have data that is into the thousands, you might want to consider implementing a pagination of some sort. If it's just a couple hundred, then I don't think you need to worry too much about the performance of a.removeAll();
I am trying to make a mobile app that inserts information into a database and while I have it pulling information and I have created my services, when I use the standard create service that Flash Builder 4.6 automatically makes, it just does not insert anything at all into the database.
I have tried everything and I am now with the following code:
I first create a variable array with the values of the service call
....
protected var Coordinatelist2:Coordinatelist = new Coordinatelist();
I then created a function to fill in the information. The variables SesID, Lat and Long are declared when my button is pressed.
....
protected function createCoordinatelist(item:Coordinatelist):void
{
Coordinatelist2.SessionID = SesID;
Coordinatelist2.Latitude = Lat;
Coordinatelist2.Longitude = Long;
createCoordinatelistResult.token = coordinatelistService.createCoordinatelist(Coordinatelist2);
}
After this, I then go and add the following line of code to the end of my button function.
.....
createCoordinatelist(Coordinatelist2);
Now, as far as I am concerned, this should then be writing to the database the items of SesID, Lat and Long using the created service token, but when I do this, nothing has entered into the database at all.
Am I doing something wrong here?
Sorry for the confusion but I came right.
What I found I had not done was commit my token once I created it. I simply used createCoordinatelistResult.token = coordinatelistService.commit(); and it worked perfectly.
Thanks for the feedback
Let's say that I have a canvas component called myCanvas and I instantiated it with
var myCanvasPage:myCanvas = new myCanvas;
this.addChild(myCanvasPage);
Then I want to essentially reload myCanvasPage later on. In effect I want to do this:
this.removeChild(myCanvasPage);
var myCanvasPage:myCanvas = new myCanvas;
this.addChild(myCanvasPage);
except instead of creating a new instance of myCanvas, I want to use the already created instance of myCanvas and essentially reload or re-create it but making sure that the instance name and references to it remain the same. What would be the best way to do this?
Whenever you do
var myCanvasPage:myCanvas = new myCanvas;
you are instantiating the myCanvasPage Object.
Removing an object from the stage will not delete the Object from memory.
As long as there is a reference somewhere in your code the myCanvasPage Object will not be garbage collected and all the values and attributes will be the same as at the time you removed it from the stage.
To make that reference you have to scope it to your class.
public var myCanvasPage:myCanvas = new myCanvas;
So now you would reference it with
this.myCanvasPage
and when you are ready to add it back to the stage.
this.addChild(this.myCanvasPage);
So to recap you can add and remove an Object from stage
this.addChild(this.myCanvasPage);
this.removeChild(this.myCanvasPage);
all day long and the data in that object will never go away.
Some good reading on garbage collection
What do you mean as "reloading"? Maybe it is simpler to create data-driven components and change that data to change or reset component state>
Woa I'm not sure where to start here... I think THE_asMan addresses most of your misunderstandings. The missing bit I think you need to look into is how a reference to an object holds (i.e. is counted) as long as it doesn't go out of scope. Just keep in mind that as long as the a variable is not out of scope, its reference to some object (if there is one, i.e. if it is not null) is counted.
http://help.adobe.com/en_US/ActionScript/3.0_ProgrammingAS3/WS5b3ccc516d4fbf351e63e3d118a9b90204-7f9d.html#WS5b3ccc516d4fbf351e63e3d118a9b90204-7f8c
I am trying to duplicate a flex component at run time.
For example if i have this
mx:Button label="btn" id="btn" click="handleClick(event)"/>
i should be able to call a function called DuplicateComponent() and it should return me a UI component thts exactly same as above button including the event listeners with it.
Can some one help me please??
Thanks in advance
Do a Byte Array Copy. This code segment should do it for you:
// ActionScript file
import flash.utils.ByteArray;
private function clone(source:Object):*
{
var myBA:ByteArray = new ByteArray();
myBA.writeObject(source);
myBA.position = 0;
return(myBA.readObject());
}
One note, I did not write this code myself, I'm pretty sure I got it from a post on the Flex Coder's list.
To solve that problem you should use actionscript and create the buttons dynamically.
Lets say you want the button(s) to go in a VBox called 'someVbox'
for (var i:uint = 0; i< 10; i++){
var but:Button = new Button();
but.label = 'some_id_'+i;
but.id = 'some_id_'+i;
but.addEventListener(MouseEvent.CLICK, 'handleClick');
someVbox.addChild(but);
}
I haven't tested it, but that should add 10 buttons to a vbox with a bit of luck.
You can't take a deep copy of UIComponents natively. You're best bet would be to create a new one and analyse the one you have to add a duplicate setup. To be honest this does sound like a bit of a code smell. I wonder if there may be a better solution to the problem with a bit of a rethink..
Same question as: http://www.flexforum.org/viewtopic.php?f=4&t=1421
Showing up in a google search for the same thing. So you've cut&pasted the same question a month later. No luck eh?
There is no easy way to do this that I know of. Many of a component's settings are dependent on the container/context/etc... and get instantiated during the creation process, so there's no reason to clone from that perspective.
You can clone key settings in actionscript and use those when creating new elements.
For instance, assuming you only care about properties, you might have an array ["styleName","width","height",...], and you can maybe use the array like this:
var newUI:UIComponent = new UIComponent();
for each(var s:String in propArray) {
newUI[s] = clonedUI[s];
}
If you want more bites on your question (rather than waiting a month), tell us what you are trying to achieve.
mx.utils.ObjectUtil often comes in handy, however for complex object types, it's typically good practice to implement an interface that requires a .clone() method, similar to how Events are cloned.
For example:
class MyClass implements ICanvasObject
{
...
public function clone():ICanvasObject
{
var obj:MyClass = new MyClass(parameters...);
return obj;
}
}
This gives your code more clarity and properly encapsulates concerns in the context of how the object is being used / cloned.
You are right but as per my understanding UI Components are not cloned by mx.utils.ObjectUtil.
from : http://livedocs.adobe.com/flex/201/langref/mx/utils/ObjectUtil.html#copy()
copy () method
public static function copy(value:Object):Object
Copies the specified Object and returns a reference to the copy. The copy is made using a native serialization technique. This means that custom serialization will be respected during the copy.
This method is designed for copying data objects, such as elements of a collection. It is not intended for copying a UIComponent object, such as a TextInput control. If you want to create copies of specific UIComponent objects, you can create a subclass of the component and implement a clone() method, or other method to perform the copy.
Parameters value:Object — Object that should be copied.
Returns Object — Copy of the specified Object
I need to read xml tags and its datas from one file and then write it to another xml..how to do it?? please let me know immediately...?
See http://livedocs.adobe.com/flex/2/langref/XML.html . I find it hard to believe you googled this before asking.
You can use the FileReference.save() method to save XML data to a local file. It will prompt the user for a location to save the file first and then save the data.
Here's an example:
var xml:XML = <root><someXmlTag/></root>;
var fileReference:FileReference = new FileReference()
fileReference.save(xml, "myfile.xml");
As far as I knew, Flex wasn't able to write to files!
I use a HTTPService to load the XML file and a result even handler to access it.
<mx:HTTPService id="service" url="myXml.xml" result="ServiceResult (event)"/>
Do not specify a result format in the HTTPService tag.
This is the code for the result event handler.
private function ServiceResult (e : ResultEvent) : void {
e.result.XmlTag.AnotherXmlTag;
}
You can also use service.lastResult to access the last result returned by the HTTPService. The result is fully compatible with the dataProvider property, especially in arrays and chart series.
var series : LineSeries = new LineSeries ();
series.dataProvider = e.result.XmlTag.AnotherXmlTag;
This will take the value in all AnotherXmlTag tags within XmlTag. For series, though, you should also specify either a yField or and xField, but it digress :-)
If it doesn't work, you can also cast it using the as keyword, example:
series.dataProvider = e.result.XmlTag as ArrayCollection;
I haven't actually tried casting it in this scenario, but the bottom line is that XML tags are vary compatible with arrays and ArrayCollections.
In your case, you would just use e.result to get the complete XML file, assign it to a variable, and write it using Ben's method. You can also create an array from individual values using the way I explained above, and manually insert tags and such if you need. The advantage of this is that you have all the values ready in an array would you need them later on. If you loop through the indices, this won't require a lot of work, and it would be the way I'd do it.
Hope this helps!