Dart Null Aware

1. Default Operator(??)

   • Imagine you have a variable called someNullableVariable, and it might have a value (it's not null), or it might be null (no value assigned to it).

   • Now, you want to use this variable to do something, but you want to make sure it has a valid value.

    var result = someNullableVariable ?? defaultValue;

1. If someNullableVariable is not null, then result will be equal to someNullableVariable. In other words, it uses the value on the left side of ?? if it exists.

2. If someNullableVariable is null, then result will be equal to default Value. In this case, it falls back to the value on the right side of ??.

2. Operational spread operator(...?)

If you're referring to the null-aware spread operator (...?), it's used to handle situations where the iterable or map might be null. It avoids a null reference error by only spreading the elements if the object is non-null.

List<int>? numbers = [1, 2, 3];
List<int> moreNumbers = [4, 5, ...?numbers];
print(moreNumbers);  // Output: [4, 5, 1, 2, 3], or [4, 5] if numbers is null

In this case, if numbers is not null, its elements are spread into moreNumbers. If numbers is null, it doesn't cause an error, and moreNumbers just contains the elements [4, 5].

If there's a specific context or usage you're referring to with "operational spread operator (...?)," please provide more details so I can offer a more accurate explanation.