How can I test if an attribute has been set in an XML node using AS3

Question

I am reading in an XML file in AS3. I need to find out if an attribute exists on a node. I want to do something like:

if(xmlIn.attribute("id")){
foo(xmlIn.attribute("id"); // xmlIn is of type XML
}

This doesn't work however. The above if statement is always true, even if the attribute id isn't on the node.

Jonathan Dunlap · Accepted Answer · 2012-01-21 00:54:48Z

18

You have to do this instead:

if(xmlIn.hasOwnProperty("@id")){
    foo(xmlIn.attribute("id"); // xmlIn is of type XML
}

In the XML E4X parsing, you have to use hasOwnProperty to check if a property for the attribute as been set on the E4X XML object node. Hope this helps!

answered Jan 21, 2012 at 0:54

Jonathan Dunlap

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2 Comments

Boundless Over a year ago

Thank you, I thought my solution was hacky. The hasOwnProperty method did the trick.

Livi17 Over a year ago

How do you check if it is empty?

marbel82 · Accepted Answer · 2013-08-09 10:24:02Z

7

I found 4 ways:

if ('@id' in xmlIn)
if (xmlIn.hasOwnProperty("@id"))
if ([email protected]() > 0)
if (xmlIn.attribute("id").length() > 0)

and I prefere first method:

if ('@id' in xmlIn) 
{
    foo(xmlIn.@id);
}

answered Aug 9, 2013 at 10:24

marbel82

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Comments

Mahmoud Badri · Accepted Answer · 2013-02-26 08:35:49Z

4

easiest way:

(@id in xmlIn)

this will return true if id attrtibute exists and false otherwise.

answered Feb 26, 2013 at 8:35

Mahmoud Badri

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1 Comment

marbel82 Over a year ago

Operator 'in' need string, you must write ('@id' in xmlIn)

Projectitis · Accepted Answer · 2016-05-18 10:21:25Z

1

I generally use:

if (xmlIn.@id != undefined)

It also works for object properties:

if (obj.id != undefined)

answered May 18, 2016 at 10:21

Projectitis

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Comments

Boundless · Accepted Answer · 2012-01-21 00:52:35Z

0

I figured this out. For anyone else having the same issue it seems like checking that the length of the attribute is greater than 0 works.

if(xmlIn.attribute("id").length() >0){
foo(xmlIn.attribute("id"); // xmlIn is of type XML
}

I don't know if this will work in all cases, but it is working for me. If there is a better way to do this please post it.

answered Jan 21, 2012 at 0:52

Boundless

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2 Comments

Jonathan Dunlap Over a year ago

Hey Boundless, see my other answer. Using hasOwnProperty is much more efficient than creating an attribute array and then count the array index to just determine if it exists. However, if performance isn't an issue, this will definitely work too.

Boundless Over a year ago

@JonathanDunlap Thanks, performance is an issue (but I still use Flash, what a shame). Your above solution with hasOwnProperty works great, thanks.

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