GSP if check on possible null object

Question

I have the following code

<g:if test="${cart == null || cart.isEmpty()}"> 
    Cart is Empty   
</g:if>
<g:else>
    ${cart.size()} items
</g:else>

but the first time I access the site (when cart is null) I get a "Cannot invoke method isEmpty() on null object" exception

Answer 1

This can be rewritten as

<g:if test="${cart}"> 
    ${cart.size} items    
</g:if>
<g:else>
    Cart is Empty
</g:else>

If a variable is null or a Lists size is 0, it will be False according to the Groovy truth.