Null Safety in Dart

Null Safety

In simple words null safety in dart means variables cannot contain null value by default. This reduces the risk of runtime bugs and makes your code error-free. This feature is called Sound Null Safety in dart. A null safety feature is added to Dart 2.12 version.

What Is Null

The meaning of Null in a programming language is no value or absence of value. For E.g int age = null;. This code will not work in dart recent version.


void main() { 
   int age = null; // give error
Show Output

Note: A value of type ‘Null’ can’t be assigned to a variable of type ‘int’.

Problem With Null

Programmers do have a lot of difficulties while handling null values. They forget that there are null values, so the program breaks. Here null mostly acts as time bomb for programmers, which is ready to break the program.


Note: Common cause of errors for programming languages, in general, comes from not properly handling null values.

Non-Nullable By Default

Variables cannot be null by default. If you attempt to assign a null value, it will give a compile-time error.

int productid = 20; // non-nullable
int productid = null; // give error

How To Define Null Value

As you know with dart sound null Safety you cannot provide a null value by default. If you are 100% sure to use it then you can use ? to the type declaration.


 int ? productid = null; // Works


void main() {
  int? age;

Important Point In Dart Null

  • Null means no value.
  • Common error in programming is caused due to null.
  • Dart 2.12 introduced sound null Safety to solve null problems.
  • Non-nullable type is confirmed to never be null.
  • You can define null value on your own if necessary.

In the next section, you will learn to handle null Safety more clearly.