Conditional Operators (??) issues in dart

Question

void main() {
  print("Conditional Operators:");
  // small if else
  var a1 = 100;
  var b2 = 20;
  var istrue = (a1 < b2) ? 'True' : 'False';
  print(istrue);

  // check if null or print name
  var name1;
  var check = name1 ?? "This is Null";
  print(check);

  var name = "Abdulelah";
  var checknot = name ?? "This is Null";
  print(name);
}

I don't how i fix this problem in line 16 yellow error said:

The left operand can't be null, so the right operand is never executed. Try removing the operator and the right operand.dartdead_null_aware_expression

problem here:var name = "Abdulelah"; var checknot = name ?? "This is Null"; print(name); — E7TRAF702, Apr 16 '22 at 17:18

score 1 · Answer 1 · answered Apr 16 '22 at 17:34

1

The variable "name" won't be NULL because you give to him the value "Abdulelah", so the right part ?? "This is NULL" won't be executed, remove this right part and the warning will disappear.

answered Apr 16 '22 at 17:34

Paulo Oyama

41
2

score 0 · Answer 2 · answered Apr 16 '22 at 18:02

Using ?? we provide default value in null case.

a = x ?? y

The above example shows that if x return/becomes null, y will be initialized on a. The fact becomes.

if x is not null, then a = x
if x is null, then a = y

Instead of using if, else we use ?? to provide null handler value.

The editor is acting smart here because it knows that name is not null, so the yellow message is saying you don't need to provide default value because left expression will never be null.

To create null variable, you need to use

DataType? variableName;

In this case you are initializing String and you can do

String? name = "Abdulelah";

But this is not needed unless you want to initialize null value on name variable.

You can check

Difference between var and dynamic type in Dart? and dart.dev for more.

Conditional Operators (??) issues in dart

2 Answers2