Custom tags: how to get the number of "child" tags

[Tiago Hillebrandt]

I like to get the number of child tags into ancestor class.

Example:

<math:bhaskara>
    <math:var name="a" value="5" />
    <math:var name="b" value="10" />
    <math:var name="c" value="20" />
</math:bhaskara>

I know that isn't the best example, but the idea is get the number of math:var tags (3 in the example) and their values into bhaskara tag.

So, how to i can make to get this values? I think that's possible through doAfterBody() in bhaskara tag, but i don't have idea how to implement this.

Thanks for all.

Regards,

Tiago

[Bear Bibeault]

The child tags can call a method in the parent tag to "register" themselves with the parent.

[Tiago Hillebrandt]

Wow, this was so easy!

Thanks Bear Bibeault

[Bear Bibeault]

Done it a few times myself!

Have you found the API that lets the children find their parent?

[Tiago Hillebrandt]

I'm using findAncestorWithClass() to get data from parent class.

And to pass data from children to parent, i created a Vector of objects at parent class, how in the follow example.

// Parent.java
private Vector<FieldObject> fieldList;

// Child.java
this.parent = (Parent) findAncestorWithClass(this, Parent.class);

FieldObject fo = new FieldObject("data");
this.parent.getFieldList().add(fo);

Is this a "correct" mode?

[Bear Bibeault]

That's the way I usually do it, with the following differences:

List is preferred over Vector.

I'd not expose the List to the child classes, but have an addChild() method on the parent that adds the child to the list which is kept private to the parent.

[Tiago Hillebrandt]

Thanks for tips

In this case, do you prefer to use List as ArrayList, LinkedList, or another?

[Bear Bibeault]

Which do you think is most appropriate in this case?

[Tiago Hillebrandt]

I think that ArrayList is the most appropriate in my case, but i'm not sure.

[Bear Bibeault]

OK, let's look at it this way, is there any reason that ArrayList would not be a good choice? What advantages over ArrayList would any of the other implementations of List have?