Flutter : What is the difference between ! , ? , ?? in Flutter and can someone please explain there use cases

MANISH 0
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I wanted to get simplest definition for Null-aware operators in Flutter with their use cases. and also which one we can use safely as per our use cases. Please try to explain the key features Null-aware operators in Flutter.

flutter-test null dart flutter
3 Answers

! is bang operator which is used to cast away nullability.

? is used to declare a property nullable.

?? is used to get the value from a variable if it is non-null or get the other value.

All examples:

int? i = 42;
print(i!.iEven); // true
int j = i ?? 0; // j = 42
iDecode0

! use when we are 100 present sure a variable have value.

? use when we are not sure our variable have value.

?? use for conditional situation. For example you have this condition :

if(x == null){
  Text('somValue');
}else {
   Text(x);
}

we can put it this way:

Text(x ?? 'somValue');
eamirho3ein0

Let me tell you the difference b/w themby examples.

  1. ? is used when you've a nullable value. Ex:
List<int>? listOfInt;

if I do try to print list[0] or list.first, it'll give me an error coz the list is nullable and the property after . will only work when the list is non-nullable. Hence we've to use ? like: list?[0] or list?.first to make sure that it'll proceed further after the . if the list is non-nullable.

print(listOfInt?.first?.toString());
  1. ! is used when the value is defined nullable but you're sure that the value is not null. Ex:
List<int>? listOfInt = [0, 1];
if(listOfInt == null) print('listOfInt is null');
print(listOfInt!.first.toString());
  1. ?? is a conditional operator used when the value is null use another value instaed. Ex:
List<int>? listOfInt = [0, 1];
print(listOfInt?.first?.toString() ?? '0');
userdUAK0
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