I'm currently using the following code in Flash Builder to return a list of variables from an XML file:
[Bindable] private var I_Authors:ArrayCollection = new ArrayCollection ();
private function init():void {
var param:Object = new Object();
param.action = "getAuthorXML";
authorService.send(param);
}
protected function authorService_resultHandler(event:ResultEvent):void
{
I_Authors = event.result.authors.author;
}
My problem is making use of this data in a dropdown list.
I have no trouble putting it into a data grid using dataProvider="{I_Authors}" and dataField="ID" etc., but all the attempts I've made to put a specific field (ID) into a dropdown list have resulted in "object Object".
I'm just starting out with flash builder so its probably a basic question but all of the tutorials I've followed on Adobe's website don't seem to be any help.
Would appreciate any advice.
Turns out you use labelField="" , just incase anyone else is a bit confused about this.
<s:DropDownList id="dropdownList" dataProvider="{________}" labelField="________"></s:DropDownList>
The problem is "author" is an object.
When you get your results from authorService you receive an object
I_Authors = event.result.authors.author;
So you have an array of objects.
You probably want to get property of your object eg.: author.ID
I_Authors = event.result.authors.author.ID;
So you have an array of author ID.
dataProvider= I_Authors
Let me know if it wasn't clear and you need more explanation.
Related
This might not be the question but it was the list of doubts which comes when learning native script from scratch.
I had a 1000 or more list of data stored in data table. know i want to display it on a list view but i don't want to read all the data at once. because i have images stored in other directory and want to read that also. So, for 20 to 30 data's the performance is quite good. but for 1000 data it is taking more than 15 minutes to read the data as well as images associated with it. since i'm storing some high quality images.
Therefore i decided to read only 20 data's with their respective images. and display it on list. know when user reaches the 15th data of the list. i decided to read 10 more data from the server.
know when i search this i came across "RadListView Load on Demand".
then i just looked at the code below.
public addMoreItemsFromSource(chunkSize: number) {
let newItems = this._sourceDataItems.splice(0, chunkSize);
this.dataItems.push(newItems);
}
public onLoadMoreItemsRequested(args: LoadOnDemandListViewEventData) {
const that = new WeakRef(this);
const listView: RadListView = args.object;
if (this._sourceDataItems.length > 0) {
setTimeout(function () {
that.get().addMoreItemsFromSource(2);
listView.notifyLoadOnDemandFinished();
}, 1500);
args.returnValue = true;
} else {
args.returnValue = false;
listView.notifyLoadOnDemandFinished(true);
}
}
In nativescript if i want to access binding element xml element. i must use observables in viewmodel or exports.com_name on associated js file.
but in this example it is started with public..! how to use this in javascript.
what is new WeakRef(this) ?
why it is needed ?
how to identify user has scrolled to 15 data, as i want to load more data when he came at 15th data.
after getting data how to update array of list and show it in listview ?
Finally i just want to know how to use load on demand
i tried to create a playground sample of what i have tried but it is giving error. it cannot found module of radlistview.
Remember i'm a fresher So, kindly keep this in mind when answering. thank you,
please modify the question if you feel it is not upto standards.
you can check the updated answer here
https://play.nativescript.org/?template=play-js&id=1Xireo
TypeScript to JavaScript
You may use any TypeScript compiler to convert the source code to JavaScript. There are even online compilers like the official TypeScript Playground for instance.
In my opinion, it's hard to expect ES5 examples any more. ES6-9 introduced a lot of new features that makes JavaScript development much more easier and TypeScript takes JavaScript to next level, interpreter to compiler.
To answer your question, you will use the prototype chain to define methods on your class in ES5.
YourClass.prototype.addMoreItemsFromSource = function (chunkSize) {
var newItems = this._sourceDataItems.splice(0, chunkSize);
this.dataItems.push(newItems);
};
YourClass.prototype.onLoadMoreItemsRequested = (args) {
var that = new WeakRef(this);
var listView = args.object;
if (this._sourceDataItems.length > 0) {
setTimeout(function () {
that.get().addMoreItemsFromSource(2);
listView.notifyLoadOnDemandFinished();
}, 1500);
args.returnValue = true;
} else {
args.returnValue = false;
listView.notifyLoadOnDemandFinished(true);
}
}
If you are using fromObject syntax for your Observable, then these functions can be passed inside
addMoreItemsFromSource: function (chunkSize) {
....
};
WeakRef: It helps managing your memory effiencetly by keeping a loose reference to the target, read more on docs.
How to load more:
If you set loadOnDemandMode to Auto then loadMoreDataRequested event will be triggered whenever user reaches the end of scrolling.
loadOnDemandBufferSize decides how many items before the end of scroll the event should be triggered.
Read more on docs.
How to update the array:
That's exactly what showcased in addMoreItemsFromSource function. Use .push(item) on the ObservableArray that is linked to your list view.
I'm planning on having multiple ace editor instances on a page and I'd like to know if the core libraries are keeping track of them so I can easily get a reference to them later.
If not, would keeping the editor instances in a dictionary or object be a good way to do it? Could I create an object on the ace class and should they be by reference or id?
var editor1 = ace.edit("myEditorDivID");
var editor2 = ace.edit("myEditorDivID2");
var editors = ace.editors;
console(editor1==editors["myEditorDivID"]); // true
console.log(editors["myEditorDivID"]); // editor1
var editorIds = ace.editorIds;
console.log(editorIds[0]); // myEditorDivID
And is there an ace destroy method that should be used to remove references to these instances?
Nevermind on part two of this question. I just found the destroy methods:
editor.destroy();
editor.container.remove();
Update:
I just thought of something else. If we can keep track of the id's or references we can prevent same id collisions. It can also help track how many editors are on a page or if multiple are being created by accident.
I just looked at the ace source and don't see anything keeping track of the editors as they are created. Should I try to whip something up or let someone else tackle it?
Update 2:
I'm thinking to add an editors property and set it by id. I've added an answer with a suggestion.
Answering my own question, no, it does not. But I suggest the following Pseudo code:
ace.addEditorById = function (id, editor) {
if (ace.editors[id]!=null) throw Error ("Editor already created");
ace.editors[id] = editor;
}
ace.getEditorById = function (id) {
return ace.editors[id];
}
ace.removeEditorById = function (id) {
var editor = ace.editors[id];
if (editor) {
editor.destroy();
editor.container.remove();
delete ace.editors[id];
}
}
ace.editors = {};
// then when I create an editor I use the following code:
editor = ace.edit("editor1");
ace.addEditorById(editor);
editor2 = ace.edit("editor2");
ace.addEditorById(editor2);
Maybe the editor can be added in the edit call. What do you think?
I am facing the following problem,
I have an object called "data". It has three properties, one of it being itemRendererData. The "itemRendererData" is an ArrayCollection of objects having many properties one of which is the property "imageURL" (datatype:String).
I am working in flex. I have defined the view and the item renderer properly. The view has the data. I am supposed to get the images from the url specified by imageURL property.
In the itemRenderer, I have declared, source
source = {data.itemRendererData.imageURL}
But the images are not being displayed.
Use a the FlexEvent.DATA_CHANGE handler rather than binding, which is actually the proper way to handle this and gives you far more control.
public function CustomItemRenderer() {
this.addEventListener(FlexEvent.DATA_CHANGE, this.dataChangeHandler);
this.addEventListener(FlexEvent.CREATION_COMPLETE, this.creationCompleteHandler);
}
private function creationCompleteHandler(e:FlexEvent) {
if (this.data) {
this.image.source = this.data.itemRendererData.imageURL;
}
}
private function dataChangeHandler(e:FlexEvent) {
if (this.data && this.initialized) {
this.image.source = this.data.itemRendererData.imageURL;
}
}
You will notice that I have a handler for FlexEvent.CREATION_COMPLETE as well. This is because the data is actually set before the components are created. So the first time a renderer is loaded, this.image is null and this.image.source will error out.
If that doesn't work, you also need to make sure that the Image/BitmapImage is not a direct child of the renderer. I never did figure out why this was, but adding it as a child of Group fixed that issue where the image was being set but not rendering. Again, I have no idea why this was and I tested for a few hours trying to figure it out.
As an added tip, avoid MXML-based ItemRenderers in mobile applications. They are noticeably slower than pure-AS3 renderers.
I'm using Linq and having trouble doing something that I believe should be trivial. I want to return data from one layer so it can be used independently of linq in another layer.
Suppose I have a Data Access Layer. It knows about the entity framework and how to interact with it. But, it doesn't care who accesses it. The one interesting requirement I have is that the queries in the entity framework return projected data that is not part of the Entity Model itself. Please don't ask me to change this part of the requirement and make POCOs for each return type, as it is not the best design given the problem I am trying to solve. Below is an example.
public class ChartData
{
public function <<returnType??>> GetData()
{
MyEntities context = new MyEntities();
var results = from context.vManyColumnsOfData as v
where v.CompanyName = "acme"
select new {Year = v.SalesYear, Income = v.Income};
return ??;
}
}
Then, I would like to have an ASP.Net UI layer be able to call into the Data Access Layer to get the data in order to bind it to a control. The UI layer should have no notion of where the data came from. It should only know that it has the data it needs to bind. Below is an example.
protected void chart_Load(object sender, EventArgs e)
{
// set some chart properties
chart.Skin = "Default";
...
// Set the data source
ChartData dataMgr = new ChartData();
<<returnType?>> data = dataMgr.GetData();
chart.DataSource = data;
chart.DataBind();
}
What is the best way to send linq projected data back to another layer?
If you don't need to use the projected type statically, just return IEnumerable<object>.
Please don't ask me to change this part of the requirement and make
POCOs for each return type, as it is not the best design given the
problem I am trying to solve.
I feel like I should rightly ignore this, as the best thing to do is to return a defined type. Anonymous types are useful when they are wholly contained within the method that creates them. Once you start passing them around, it is time to go ahead and give them the proper class treatment.
However, to live within your imposed limitations, you can return IEnumerable<object> from the method and use that or var at the callsite and rely upon the dynamic binding of the control to get at the data. It's not going to help you if you need to deal with the object programmatically, but it will serve fine for databinding.
You can not return an anonymous type, so basically for this you will need POCO's even though you don't want them.
"not the best design given the problem I am trying to solve"
Could you explain what you are trying to achieve a little more? It might be possible to return some type of list containing a dictionary of items (ie rows and columns). Think something like an untyped dataset (yuck)
Your GetData method can use IEnumerable (the "old" non-generic interface) as its return type.
Any dynamic resolution (e.g. ASP.NET or XAML bindings) should work as expected, which seems to be what you want to do.
However, if you want to use the results in your code, you will probably have to resort to .NET 4's dynamic keyword.
The following example can be run in LINQPad (in "C# Program" mode) and illustrates this:
void Main()
{
var v = GetData();
foreach (dynamic element in v)
{
((string)element.Name).Dump();
}
}
public IEnumerable GetData()
{
return from i in Enumerable.Range(1, 10)
select new
{
Name = "Item " + i,
Value = i
};
}
Keep in mind that, design-wise, coding like this will make most people frown and can affect performance.
I need to store and retrieve lists in PhoneApplicationService.Current.State[] but this is not a list of strings or integers:
public class searchResults
{
public string title { get; set; }
public string description { get; set; }
}
public List<searchResults> resultData = new List<searchResults>()
{
//
};
The values of the result are fetched from internet and when the application is switched this data needs to be saved in isolated storage for multitasking. How do I save this list and retrieve it again?
If the question really is about how to save the data then you just do
PhoneApplicationService.Current.State["SearchResultList"] = resultData;
and to retrieve again you do
List<searchResults> loadedResultData = (List<searchResults>)PhoneApplicationService.Current.State["SearchResultList"];
Here is a complete working sample:
// your list for results
List<searchResults> resultData = new List<searchResults>();
// add some example data to save
resultData.Add(new searchResults() { description = "A description", title = "A title" });
resultData.Add(new searchResults() { description = "Another description", title = "Another title" });
// save list of search results to app state
PhoneApplicationService.Current.State["SearchResultList"] = resultData;
// --------------------->
// your app could now be tombstoned
// <---------------------
// load from app state
List<searchResults> loadedResultData = (List<searchResults>)PhoneApplicationService.Current.State["SearchResultList"];
// check if loading from app state succeeded
foreach (searchResults result in loadedResultData)
{
System.Diagnostics.Debug.WriteLine(result.title);
}
(This might stop working when your data structure gets more complex or contains certain types.)
Sounds like you just want to employ standard serialisation for your list object, see here in the MSDN docs
http://msdn.microsoft.com/en-us/library/ms973893.aspx
Or also XML serialisation if you want something that can be edited outside of the application (you can also use the Isolated Storage exploter to grab the file off and edit later)
http://msdn.microsoft.com/en-us/library/182eeyhh(v=vs.71).aspx
Alternatively i would also suggest trying out the Tombstone Helper project by Matt Lacey which can simplify this for you greatly
http://tombstonehelper.codeplex.com/
The answer by Heinrich already summarizes the main idea here - you can use the PhoneApplicationService.State with Lists like with any objects. Check out the MSDN docs on preserving application state: How to: Preserve and Restore Application State for Windows Phone. There's one important point to notice there:
Any data that you store in the State dictionary must be serializable,
either directly or by using data contracts.
Directly here means that the classes are marked as [Serializable]. Regarding your List<searchResults>, it is serializable if searchResults is serializable. To do this, either searchResults and all types referenced by it must be marked with the [Serializable] OR it must be a suitable Data Contract, see Using Data Contracts and Serializable Types. In short, make sure the class is declared as public and that it has a public, parameterless constructor.