FormAPI: How to clear combobox

Hi!

I am FormAPI-controlling the values of a combobox and quite puzzled how you can reset it to NULL (the initial empty item of a combobox). None of these work: setValue(null), setValue(""), etc... Anybody an idea whats the trick here?

Thanks for any hint Smiley Happy

Regards

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Migrateduser

There's a few different ways and drop-down lists are different animals than other form elements. If your drop-down has retained the null option -- that is, if there's an empty option at the top of your drop-down list, you could try something like:

IWItem.combo.options[0].selected = true;

-- I believe that's the code. My Javascript might be a bit off but I'm hoping the point is clear.

Otherwise, if you're looking to actually CLEAR the drop-down list, which your subject sounds like you want to do even though your post seems to imply otherwise, do IWItem.removeOption(x) where x is the index number of the element you want to clear. So:

for (var i = 1; i<=IWItem.combo.getOptions().length; i++) {
IWItem.combo.removeOption(i);
}

ravio

Hi!

I am FormAPI-controlling the values of a combobox and quite puzzled how you can reset it to NULL (the initial empty item of a combobox). None of these work: setValue(null), setValue(""), etc... Anybody an idea whats the trick here?

Thanks for any hint
Regards

The issue is not quiet clear to me.
so, I am going to make it what I think it is ;-) and so,

Values of multiple combo box items are like an array.
And you can try:item.setValue([0]);

ninickname

Thanks for your quick response, dave.

I tried it out

IWDatacapture.getItem("/mydropdown").options[0].selected=true;

But receive a JavaScript error that "options" doesnt have any properties (the dropdown clearly shows the empty default and my two options).
This is TS 6.5 on W2K by the way.
And I stumbled upon some other forum message that there seem to be bugs in the options handling?
You mentioned other ways of taming this animal?

ninickname

Hello ravio,

also thanks for your suggestion

IWDatacapture.getItem("/mydropdown").setValue([0]);

unfortunately also doesnt do anything Smiley Sad

ravio

Aha!
If this is a dropdown combo, Try :item.setValue(0);
Also,Is this item inside a replicant?

ninickname

No replicant.
I tried that also, but index 0 of course refers to the first of MY elements (which works fine). the empty (null) element is above it.

None of these seem to work:

setValue(null)
setValue("")
setValue()
setValue(-1)
setValue([0])
options[0].selected=true

(Background: I *need* an empty field as an option for the user. BUT: If I add one on my own, this way I get TWO empty optons; TeamSites builtin and mine.)

Migrateduser

I found this in the FormAPI documentation:

[left]Even though this blank entry is physically present in the list to enable the user to make no selection, it is not returned by the FormAPI option methods.

So, that's bad but what if you were to start without a blank option (by assigning a default selected value) and then insert the blank option?

For instance:


< select >
  < option value = 'null' label = '' / >
  < option value = '1' label = '1' selected = 't' / >
< / select >

This way, FormAPI will "know" about your blank option and there will be only one because of your "selected='t'". Then, to select the first option, which is now blank, you would setValue(0).

[/left]

jbonifaci

You're going to want to read up on getOptions() and setOptions(). This is the best way to manipulate multi select items.

ninickname

Thanks for all these ideas!
-->
This way I get two empty options at the beginning of the list

(1) FormPublishers *null* value empty label (obviously not in the array)
(2) My own empty label with value "null" (string)

Doesnt do the trick.
Quite unbelievable this situation....

---------------------------------------------

Also the documentation seems wrong...

"If a single item has no value (and no default value), FormsPublisher renders the select list with an extra blank option at the top."
implies that IF I HAVE A DEFAULT VALUE that empty blank option would not show up. ... well, it *does*...

Migrateduser

You didn't really read the thread, did you? The documentation explicitly states that FormAPI does not "know" about the blank option which displays with a select box except when a default value is selected.

ninickname

My last post was cut off at the point where I actually stated that. -> I used a default value and the blank option *still showed up*! Since the customer's wish was also to have the empty field as default, this seems to me like an unsolveable challenge.
- No matter what options configuration I choose FPublisher always adds a blank option on top
- The blank option can not be write-accessed through FormAPI (read can do, because I get a null value Smiley Happy

), meaning I can through FormAPI not SET the dropdown to the blank option
Only work around really seems to live with two empty options (one is my own that I can handle as much as I like)

Thanks guys for finding that out :-)

jbonifaci

I believe you need to make the field required in the DCT to not have the blank option show up.

~Jeff

Migrateduser

Try posting again. It seems that the "new and improved" DevNet is horrible with posting code, something which people like us do quite often. When I did it earlier in the thread, I had to go back and put spaces between my < > and the tags' contents.

Migrateduser

Jeff, not true.

I have DCTs in which a drop-down list is required but I still have the blank option. This is fine for my requirements but simply setting required to true doesn't solve this. According to the documentation (and stated earlier in the thread, interestingly enough), if you set a default value for the drop-down list, you lose the blank option.

ISCBorisB

Jeff, not true.

I have DCTs in which a drop-down list is required but I still have the blank option. This is fine for my requirements but simply setting required to true doesn't solve this. According to the documentation (and stated earlier in the thread, interestingly enough), if you set a default value for the drop-down list, you lose the blank option.

To clear combo box:

var cmb = IWDatacapture.getItem("/combo");
var cmb_options = cmb.getOptions();
if (cmb_options != null) {
for (var i = 0; i<cmb_options.length; i++) {
cmb_options.selected = false;
}
cmb.setOptions(cmb_options);
}

Not sure if that's 100% IW Suppotred...

Migrateduser

Thanks for that... that's the classic method to do that in straight Javascript but Interwoven has implemented the removeOption() method to alleviate a few of those lines.

But ninickname's original question was about setting the selected value to "the blank option" after some event (I think I have that right).

ISCBorisB

Thanks for that... that's the classic method to do that in straight Javascript but Interwoven has implemented the removeOption() method to alleviate a few of those lines.

But ninickname's original question was about setting the selected value to "the blank option" after some event (I think I have that right).

- removeOption clears drop-down list element
- what I posted clears customer's choice
- do not see any issue with doing either on required event

Migrateduser

Since we're beating this issue to death, removeOption(x) removes ONE option at a time from the drop-down list, indicated by index number 'x'. It would only clear the entire list if you had one option to begin with.

jbonifaci

Jeff, not true.

I have DCTs in which a drop-down list is required but I still have the blank option. This is fine for my requirements but simply setting required to true doesn't solve this. According to the documentation (and stated earlier in the thread, interestingly enough), if you set a default value for the drop-down list, you lose the blank option.

Dave, I was replying to ninickname's post where he said he was setting a value as selected and he was still getting the blank option. I was telling him he must also make the item required to get the blank space to disappear. You have to do both to get it to disappear.

~Jeff

Migrateduser

Okay, no worries -- I may have misunderstood based on the timing of your post, etc. But the information I relayed was based on the documentation which, as we all know, is questionable at best (p. 18 6.5 FormAPI):

[left][font=Perpetua][left]If a single
< select >
item has no value (and no default value), FormsPublisher renders the select list with an extra blank option at the top.

Even though this blank entry is physically present in the list to enable the user to make no selection, it is not returned by the FormAPI option methods. If a single
< select >
or
< radio >
item is unselected,
getValue()
returns null. Calling
setValue(0)
selects the first non-blank option; calling
removeOption(0)
removes the first non-blank option. The options array returned by
getOptions
does not include the blank option.

Because FormsPublisher uses the empty string to represent the case of no selection, options should not have empty values. If they do, options with empty values are treated as if no selection was made.

Multiple
< select >
items are unaffected by this behavior because they “natively” support the empty selection when none of their options are selected. If a multiple
< select >
has no option selected,
getValue()
returns an empty array.

[/left]

[/font]

[/left]

ISCBorisB

Simply inexact wording in my previous post - I do know that removeOption clears only one, you have to use it in a loop ad infinitum...

Migrateduser

No problem -- I think if one needed to extract one option from the drop-down list, I think removeOption() is a better choice. However, the code you provided is definitely preferred if the entire list needs to be rebuilt. When you get into hundreds or thousands of options in a drop-down, it can be very heavy on the client to rebuild the list when only one item needs to be changed.

Then again, I'm not familiar with the internals of removeOption(). I don't think that it does this but perhaps it also rebuilds the list, I'm not sure.

Anyway, just my opinion.

Bjorn

Thousands of options in a drop-down?!

Migrateduser

Sure! I've seen it and I'm sure there are hundreds of examples on the internet where such an obsene drop-down list is being used. Oh... actually, I have a 700-element drop-down list on my personal site for a one-action navigation thing but it gets very client-heavy when too many JS actions are associated with such a large drop-down list. Let's keep in mind that Internet Explorer, still the most popular web browser, is made by Microsoft -- a company well known for software that crashes at the drop of a hat... or the stroke of a key.