adding elements to empty json array and removing them - json

I have created an empty json object having an array itemlist(which further contains itemid and title of an item) by this:
var jsonObj = {};
jsonObj.itemlist=[];
jsonObj.itemlist.push({});
Firstly, have i done the declaration correctly?
Secondly, the title and itemid are generated dynamically so i need to add them to the itemlist array. I tried this but it keeps only one array element:
jsonObj.itemlist['title']=gentitle;
jsonObj.itemlist['itemid']=genitemid;
How can i add multiple elements (not all at once) if i have an empty array of itemlists?
Also, i also need to remove a particular array element based on the title of the element. How can that be done? I think the splice and delete function can be used for this, but how can i find the index of that element?

since you already pushed a empty object into the array, you need to modify that object:
jsonObj.itemlist[0]['title']=gentitle;
jsonObj.itemlist[0]['itemid']=genitemid;
To add more objects, you can do the same thing: push in an empty object, then modify that object. Or, you can create an object, modify it, then push it into the list.
var new_obj = {'title':gentitle, 'itemid':genitemid};
jsonObj.itemlist.push( new_obj );
To delete objects with certain attribute value:
for (var i = jsonObj.itemlist.length-1; i >= 0; i--)
if(jsonObj.itemlist[i]['title'] == "to-be-removed")
jsonObj.itemlist.splice(i,1);
Note that you need to go backward, otherwise the splice will mess up the array indexes

Related

Remove Value from JSON array

How do I remove a value from a JSON array? Say I have an array like
var my_array = [3,6,4,8,11]
and I want to remove the number 4 from the array. I have tried delete my_array(4) but that just removes index 4 and apparently it doesn't delete it, it leaves a NULL gap in its place. I simply need to remove the number out of the array entirely. But I don't know at what index that number is positioned so I can't use something like splice.
You must find index of what you need first..
var my_array = [3,6,4,8,11]
var will_delete = my_array.indexOf(4);
my_array.slice(will_delete,1)
Please confusion splice and slice
Splice : https://www.w3schools.com/jsref/jsref_splice.asp
Slice : https://www.w3schools.com/jsref/jsref_slice_array.asp

Flash AS3 How to display a random item from an xml list then remove that item from the list so it will not be reused

I'm using Flash AS3 trying to display random questions from an xml list on stage. When the user clicks an option it should move on to another question but the one they got should be removed from the list so it will not come back.
I have the randomize part okay but can't figure out how to remove the question from the list.
Here is the section I have.
function randomizeQuestion():void {
var numOfQuestions:Number = xmlData.item.length();
var shuffledNumbers:Array = new Array(randomAns.length);
var randomPos:Number = 0;
//Randomizes selected question
currentQuestion = int(Math.random() * numOfQuestions);
//Randomizes answer numbers
for (var i:int = 0; i < shuffledNumbers.length; i++)
{
randomPos = int(Math.random() * randomAns.length);
shuffledNumbers[i] = randomAns.splice(randomPos, 1)[0];
}
randomAns = shuffledNumbers;
correctAns = xmlData.item[currentQuestion].children().(hasOwnProperty("#correct"));
}
Try to get index:
correctAnsIndex = xmlData.item[currentQuestion].children().(hasOwnProperty("#correct")).childIndex();
or if more elements, to get first one:
correctAnsIndex = xmlData.item[currentQuestion].children().(hasOwnProperty("#correct"))[0].childIndex();
then use delete where appropriate, like here:
delete xmlData.item[correctAnsIndex];
I would add another array to your code in which you can store all the questions that are eligible. As a question gets asked, remove it from that array. So you'll have one array of allQuestions and another array of eligibleQuestions. allQuestions can just be a comprehensive list. Then, push all the questions you want to go through into the eligibleQuestions array. As the questions get answered, splice them from the array.
It would be good to also share an example of your XML file that you're loading, but let's use the example below.
<data>
<item>
<question></question>
<option1></option1>
<option2></option2>
</item>
<item>
<question></question>
<option1></option1>
<option2></option2>
</item>
</data>
Based on the code you have, I assume your function is being called each time you want to randomize a question.
Now what you'd want to do is create an array that holds the number of <item> tags you have outside of this function so that you can remove values from it whenever you want.
You can create this var numOfQuestions:Array = new Array(); as a global variable and then initialize it using a loop before you enter the randomizeQuestions() function.
for(var i = 0; i < xmlData['item'].length(); i++)
{
numOfQuestions.push(i);
}
Basically this array will serve as a method of calling a specific item and removing it from the program without altering the actual XML file in any way.
Then whenever you wish to remove an element you use
numOfQuestions.splice(numOfQuestions.indexOf(valueToBeRemoved), 1);
This will search the array for the element you wish to remove and then remove it from the array.
Lastly the randomizeQuestion function has to be modified.
currentQuestion = int(Math.random() * numOfQuestions.length); //since numOfQuestions is now an array instead of a Number

How do i populate an Array in one class based on a textfield in another class?(Actionscript 3.0)

i have a class (TheList.as). in which i have an array "Data" and it has a couple of values. Then i have a loop through which i am creating a scrollable list which uses the values from "Data" array. [I am trying make a unit converter]
Then i have another class "Units.as". In that class i have created three instances of "TheList". A main list ("myList"), and to sublists "ListFrom" and "ListTo". They are using values from "Data" array. Now i have text field whose value changes to whatever item is clicked. When i click "Angle" in the main list, i want the sublists to get populated with ("Degree", "Radian" etc)..
Here is what i tried
if(myList._TextLabel.text == "Angle")
{
ListFrom.Data = ["Degree", "Radian"];
}
But nothing happens, i do not get any error either. When i do this in an "ENTER_FRAME" event and trace (ListFrom.Data), i can see that the values change, but they do not get assigned to the list items in the list. I would really appreciate the help. Thanks!
Here are complete Classes for understanding the situation better(the code is pretty messy, as i am a newbie to OOP)
TheList.as: http://pastebin.com/FLy5QV9i
Units.as : http://pastebin.com/z2CcHZzC
where you call ListFrom.Data = ["Degree","Radian"], make sure when the data changed, the renders in the ListFrom have been set new data. for example, you may use MyRender in ListFrom for show, you should debug in the set data method in MyRender.
you should call the code below after you call ListFrom.Data = ["Degree","Radian"];
for (var i:int = 0; i < Data.legnth;i++) {
var render:MyRender = ListFrom[i] as MyRender;
if (render) {
render.data = Data[i];
} else {
var render:MyRender = new MyRender();
render.data = Data[i];
ListFrom.addChild(render);
}
}
You can use event listeners, singleton classes or reference one class to another, depending on the style you want. All are equally valid and fast / efficient.

AS3 stack overflow?

Working with Arrays. I create objects on a Class base, push them into an Array, I have 2 buttons: one adds a Child and pushes it into the Array, second one Shifts Array and removes the Child. Also a function on my mouse, if I click an object, I define it's Array number, remove the Child and... well, not sure if successful but "delete Array[i];" where i is target's Array number. I can see Array.length in a text field every time I do something. Second button actually does remove an object from Array, the number decreases. But deleting a specified object from the Array, as well as Array.slice(i,1), doesn't reduce the Array length. So I'm afraid it may cause overflow. It's only Array, not sure, maybe it's fine to have over a million cells in an Array? Like if I make a game with meteor shower, meteors are removed from the screen, but the Array still has their cells. And if they appear like 30-50 per sec, it's obvious I may get memory problems in 20 minutes of running it. Well it's 60k so maybe I shouldn't worry as only graphics take much memory?
Still, I could use an advice on how to shift an object in a middle of an Array. Chosen one. How do I delete it as if it never was created, same as Shift does? (it does, right?)
Array.splice() will do most of the tricks. As you remove the meteor off screen, you can splice it out of the array, do like this:
var i:int=meteorArray.indexOf(meteorToRemove);
if (i>=0) meteorArray.splice(i,1);
You should not create a new object as a good practice if you are deleting other. Try recycling, or better said 'object pools'
You should figure out the number max of elements you may use at once. create a property 'active' on each and set it to true or false instead of creating/deleting. Then you can run the update on each object and update it only if necessary
For example:
var meteors:Array = [];
// create 500 meteors
for ( var i:int = 0; i < 500; i++ ) {
var meteor:Meteor = new Meteor();
meteor.active = false;
meteors.push(meteor);
}
// enable one meteor
meteors[0].active = true;
// in your update method:
for each (var meteor in meteors )
if ( meteor.active )
meteor.update();
Hope that helps.
Also you can add a helper method to get a meteor available:
function getMeteorAvailable():Meteor
{
for each (var meteor in meteors )
if ( !meteor.active )
return meteor;
}

Splice then re-index array in ActionScript 3

I want to remove the first four indexes from the array using splice(), then rebuild the array starting at index 0. How do I do this?
Array.index[0] = 'one';
Array.index[1] = 'two';
Array.index[2] = 'three';
Array.index[3] = 'four';
Array.index[4] = 'five';
Array.index[5] = 'six';
Array.index[6] = 'seven';
Array.index[7] = 'eight';
Array.splice(0, 4);
Array.index[0] = 'five';
Array.index[1] = 'six';
Array.index[2] = 'seven';
Array.index[3] = 'eight';
I am accessing the array via a timer, on each iteration I want to remove the first four indexes of the array. I assumed splice() would remove the indexes then rebuild the array starting at 0 index. it doesn't, so instead what I have done is created a 'deleteIndex' variable, on each iteration a +4 is added to deleteIndex.
var deleteIndex:int = 4;
function updateTimer(event:TimerEvent):void
{
Array.splice(0,deleteIndex);
deleteIndex = deleteIndex + 4;
}
What type of object is "Array" in the code you have shown? The Flash Array object does not have a property named "index". The Array class is dynamic, which means that it let's you add random properties to it at run time (which seems to be what you are doing).
In any case, if you are using the standard Flash Array class, it's splice() method updates the array indexes automatically. Here is a code example that proves it:
var a:Array = [1,2,3,4,5];
trace("third element: ", a[2]); // output: 3
a.splice(2,1); // delete 3rd element
trace(a); // output: 1,2,4,5
trace(a.length); // ouput: 4
trace("third element: ", a[2]); // output: 4
If I am understanding what you want correctly, you need to use the unshift method of Array.
example :
var someArray:Array = new Array(0,1,2,3,4,5,6,7,8);
someArray.splice(0,4);
somearray.unshift(5,6,7,8);
Also, you are using the Array Class improperly, you need to create an instance of an array to work with first.
The question is confusing because you used Array class name instead of an instance of an array. But as the commenter on this post said, if you splice elements, it automatically re-indexes.
im not sure what you want to do, but Array=Array.splice(0,4) should fix somethin..