Assert in Dart
Assert
While coding, it is hard to find errors in big projects, so dart provide a assert method to check for the error. It takes conditions as an argument. If the condition is true, nothing happens. If a condition is false, it will raise an error.
Syntax
You can use assert without a custom message or with a custom message.
assert(condition);
// or
assert(condition, "Your custom message");
Example 1: How To Use Assert In Dart Program
This example shows how you can use assert without a custom message.
void main() {
var age = 22;
assert(age!=22);
}
Run Online
Example 2: How To Use Assert In Dart Program
This example shows how you can use assert with a custom message.
void main() {
var age = 22;
assert(age!=22, "Age must be 22");
}
Run Online
How to Run File In Assert Mode
Use this command to run the dart file, which enables assert. If you don’t use this, you will not be able to see the issue. You can use this command below if you are running a dart file from the computer.
dart --enable-asserts file_name.dart
Note: The assert(condition) method only runs in development mode. It will throw an exception only when the condition is false. If the condition is true, nothing happens. Production code ignores it.
Video
Watch our video on the assert in Dart.