Basics in for loop in actionscript 3 in flex

Question

Good Morning stackoverflow... I'm having a problem.... this is my sample code

var i:Number = new Number();

trace("showarray length" + showArray.length);

for(i=0;i<showArray.length;i++){

    trace("equal daw" + showArray.getItemAt(i).id + "==" + num);

    if(showArray.getItemAt(i).id == num){
        showArray.removeItemAt(i);

    }
}
trace('alerts');

myproblem here is...wherenever the if is satisfied it stops looping it immediately goes out of the loop

this is a sample output given that the length of showArray is 2 and num = 0

showarray length2

equal daw0==0

alerts

please help me

alxx · Accepted Answer · 2011-03-23 18:09:22Z

8

If you want to remove items while iterating over array, iterate in reverse order. This way element removal does not affect cycle condition:

for (var i:int = showArray.length - 1; i >= 0; i--) {
    if (someCondition) {
        showArray.removeItemAt(i);
    }
}

Another small bonus that this is slightly faster, as it doesn't call showArray.length on each step.

answered Mar 23, 2011 at 18:09

alxx

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1 Comment

Drenai Over a year ago

Agree, have to iterate in reverse: answered very similar here: stackoverflow.com/questions/4946007/…

Manish · Accepted Answer · 2011-03-23 19:26:28Z

3

An even better way might be to use the filter method of the Array class.

array = array.filter(function (e:*, i:int, a:Array):Boolean {
        return e.id != num;
    });

answered Mar 23, 2011 at 19:26

Manish

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Comments

dain · Accepted Answer · 2011-03-23 18:02:53Z

1

When your if is satisfied for id == num (which is 0 so happening in the first loop) and the item is removed, your array length decreases to 1 so the loop won't run any more.

answered Mar 23, 2011 at 18:02

dain

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Comments

Lucas Gabriel Sánchez · Accepted Answer · 2011-03-23 20:19:16Z

1

That's because you are removing items at the time you are iterating throught them.

array = [1, 2]
         ^         // pointer in first iteration

eliminate 1
array = [2]
         ^         // the pointer remains in the same location

//ups! out of the loop. all items were visited.

You can copy the array before you iterate through it and iterate the copy or mark the indices to remove and remove them later or iterate the array backwards.

PS: Sorry for my poor English.

edited Mar 23, 2011 at 20:19

answered Mar 23, 2011 at 18:03

Lucas Gabriel Sánchez

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1 Comment

divillysausages Over a year ago

Copying the array is unnecessary and slow, when you can just iterate through it backwards and have no problem

Josh Tynjala · Accepted Answer · 2011-03-23 22:54:54Z

1

After showArray.removeItemAt(i);, add i--;

Because you removed the item at index i from the array, the item that was at i + 1 got moved to i. By subtracting one, you ensure that the moved item doesn't get skipped.

alxx's answer is also a good solution.

answered Mar 23, 2011 at 22:54

Josh Tynjala

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