How to check for null in Twig

Question

What construct should I use to check whether a value is NULL in a Twig template

User · Answer

Without any assumptions the answer is      if var is null      But this will be true only if var is exactly NULL  and not any other value that evaluates to false  such as zero  empty string and empty array   Besides  it will cause an error if var is not defined  A safer way would be      if var is not defined or var is null      which can be shortened to      if var default is null      If you don t provide an argument to the default filter  it assumes NULL  sort of default default   So the shortest and safest way  I know  to check whether a variable is empty  null  false  empty string array  etc       if var default is empty

User · Answer

Depending on what exactly you need    is null checks whether the value is null      if var is null           do something       endif     is defined checks whether the variable is defined      if var is not defined           do something       endif       Additionally the is sameas test  which does a type strict comparison of two values  might be of interest for checking values other than null  like false       if var is sameas false            do something       endif

User · Answer

test if varibale exist         if var is defined               todo         endif            test if variable is not null         if var is not null               todo         endif

User · Answer

How to set default values in twig  http   twig sensiolabs org doc filters default html     my var   default  my var doesn t exist        Or if you don t want it to display when null      my var   default

User · Answer

I don t think you can  This is because if a variable is undefined  not set  in the twig template  it looks like NULL or none  in twig terms   I m pretty sure this is to suppress bad access errors from occurring in the template   Due to the lack of a  identity  in Twig       this is the best you can do     if var    null        stuff in here    endif      Which translates to   if   isset  context  somethingnull       context  somethingnull     null     null      echo  stuff in here       Which if your good at your type juggling  means that things such as 0      FALSE  NULL  and an undefined var will also make that statement true   My suggest is to ask for the identity to be implemented into Twig

User · Answer

Also if your variable is an ARRAY  there are few options too      if arrayVariable 0  is defined          if variable is not null     endif      OR     if arrayVariable length  gt  0          if variable is not null      endif      This will only works if your array is defined AND is NULL

User · Answer

You can also use one line to do that      yourVariable is not defined    Not Assigned     Assigned

User · Answer

you can use the following code to check whether     if var is defined     var is variable is SET     endif

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