Can E4X Get Attribute of a Parent Node Based on Attribute of a Child At Any Level?

问题

Consider this XML snippet with "nodes" which can have unlimited child levels of "subnode" elements.

I want to find @type attribute of the node for any given subnode, based on its @id attribute. For example, if I have an id of 9 then I want to return the type="foo" from above.

<xml>
    <node type="bar">
        <subnode id="4">
            <subnode id="5"/>
        </subnode>  
        <subnode id="6"/>
    </node>
    <node type="foo">
        <subnode id="7">
            <subnode id="8">
                <subnode id="9"/>
            </subnode>
        </subnode>
        <subnode id="10"/>
    </node>
</xml>

The E4X I have come up with, but which fails is:

xml.node.(subnode.(@id == '8')).@type

I can kind of see why it doesn't work. What would make more sense is the following but the syntax fails (in AS3):

xml.node.(..subnode.(@id == '8')).@type

How can this be done?

回答1:

You should be able to get the type value using this E4X:

xml.node.(descendants("subnode").@id.contains("8")).@type;

回答2:

Try this

for each(var node:XML in xml.node)
{
    var subnodes:XMLList = node..subnode;
    if(subnodes.(@id == '9').length() != 0)
        return node.@type;
}

EDIT: Even this should work:

if(node..subnode.(@id == '9').length() != 0)

回答3:

Having given up on E4X I used a "hack" and did it in ActionScript instead. Here's how:

var p:XML = xml..subnode.(attribute('id').toLowerCase() === "8")[0];

//Traverse back up to the parent "node"           
while ( p.name().toString() === "subnode" ) {
    p = p.parent();
}

Alert.show(p.@type); //Should say "foo"

Seems a mess though. Would still be interested in any plain E4X solution.

来源：https://stackoverflow.com/questions/1427810/can-e4x-get-attribute-of-a-parent-node-based-on-attribute-of-a-child-at-any-leve

标签

actionscript-3

apache-flex

e4x