I am trying to check value using if but the app crash on that line. I am using flutter.

 if (value == null || value.isEmpty || !value.contains('@')) {
          return 'Please enter a valid email.';
        }

getting that Error: Property 'isEmpty' cannot be accessed on 'String?' because it is potentially null. Try accessing using ?. instead.

CodePudding user response：

Replace

value.isEmpty

With

(value.toString()).isEmpty

CodePudding user response：

You should add null check for both value!.isEmpty and value!.contains('@'). Like this:

if (value == null || value!.isEmpty || !value!.contains('@')) {
   return 'Please enter a valid email.';
}

or as esentis suggessted:

if ((value?.isEmpty ?? true) || !value!.contains('@')) {
   return 'Please enter a valid email.';
}

CodePudding user response：

Adding my comment as answer so you can have better view of it:

 if (value == null || ( value?.isEmpty ?? true ) || (!value?.contains('@') ?? true )) {
          return 'Please enter a valid email.';
 }

CodePudding user response：

Do this instead

if((value != null && value.isEmpty()) || (value == null)){

}