How can I check if field is null or empty in DWT?

Question

I'm making a DWT component template that loops multivalued componentlinked components. I want to check if a textfield in a linked component is empty, but it always gives errors. I need to use the Dreamweaver Get extention, because otherwise I can't get to my deepest linked properties:

<!-- TemplateBeginRepeat name="Component.Fields.AfbeeldingLink" -->

<img  src="@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding")@@" alt="@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding.Metadata.AltTekst")@@" />

<!-- TemplateEndRepeat -->

This works fine. But now I want to check if a property like

@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding.Metadata.AltTekst")@@

is empty to do something different. How can I do that? This always gives errors:

<!-- TemplateBeginIf cond="StringLength(@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding.Metadata.AltTekst")@@) > 0" --> 

Like ' a ; is needed'.

Does anybody has an idea ?

Kind regards, Herman

Answer 1

When calling TemplateCallable methods from within Conditions, don't use @@ . Simply use the method name as :

<!-- TemplateBeginIf cond="Get(...) !=''" -->

I had few TemplateCallable custom methods implemented as well and the below syntax always worked for checking if the AltText field is Empty or NOT

<!-- TemplateBeginIf cond="GetMetaDataFieldValue(Component.ArticleImage,'AltText') !=''" -->

The method GetMetaDataFieldValue has return type of Stringand using !='' always worked. Note that there is NO space inbetween the single quotes in !=''

The Dreamweaver's Get() method's return type is String as well.

Answer 2

Generally speaking checking for empty fields or null values in DWT TBBs means you need to check if the value contains an empty string, so:

<!-- TemplateBeginIf cond="@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding.Metadata.AltTekst")@@ == ''" -->

But its been too long for me to remember if the Get extension actually was able to return you empty strings for non existing fields (since when a field is empty, it doesn't have an element in the XML)

You might need to extend the Get extension with a IsEmpty() method, which is something I would actually do anyways, since that will clean up your Template code in a great way:

<!-- TemplateBeginIf cond="@@IsEmpty("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Afbeelding.Metadata.AltTekst")@@" -->

Well okay not "great", but slightly better, if you want something decent, readable and understandable, I would take a look at DXA and ditch DWT Templating alltogether ;o).

UPDATE

Good point to mention you got the error when trying to use @@ inside a condition, now that my memory of DWT Templating is refreshing, I seem to recall there was a limitation we had with custom functions, being that they could not be used in a condition. So looks like my answer will not help you at all, apart from the last bit ;o)

But since I'm digging from memory of years ago (which is likely to be only partially correct), I might still be wrong on this, you could give it a try without the @@ signs in the condition.

Answer 3

Thanks all for your help, I finally got it working!

It seems that when my value was empty, the get-function returned 'undefined'. Also, the single quote-solution from above helped, then I got no errors when I surrounded the @@Get@@ with single quotes. The working example is this one:

<!-- TemplateBeginIf cond="'@@Get("Fields.AfbeeldingLink[${TemplateRepeatIndex}].Fields.Link.ExterneLink")@@'!='undefined'" -->

Kind regards and big thanks! Herman

Answer 4

I think this is just due to missing quotes.

StringLength(@@Get("your_field_path")@@)

will likely render to:

StringLength(This is my field value)

This will error since the rendered string isn't in quotes.

Try adding single quotes:

StringLength('@@Get("your_field_path")@@')

Also you may not even need StringLength, you could probably get away with

<!-- TemplateBeginIf cond="'@@Get("your_field_path")@@'" -->

I'll pre-empt a "gotcha". If your field contains a quote then this will likely break (since you're effectively rendering into a condition then trouble is likely to follow!).