Keywords in Dart

Keywords in Dart

Keywords in Dart

Keywords are reserved words that have a specific meaning to the compiler and cannot be used as identifiers (names for variables, functions, classes, etc.).

Examples of keywords include class, const, for, if, void, and while. We we understand them fully once we use them in our code in the upcomming lessons.

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List of Keywords

Keyword Description
abstract Used to declare a class as abstract.
as Used to specify a library prefix or as a type cast.
assert Used to assert that a condition is true.
async Used to specify that a function, method or block of code is asynchronous.
await Used to suspend execution until an asynchronous operation completes.
break Used to terminate the execution of a loop, switch statement or labeled statement.
case Used to define a specific condition in a switch statement.
catch Used to specify a block of code to be executed, if an error occurs in the try block.
class Used to declare a class.
const Used to declare a variable as a compile-time constant.
continue Used to continue the execution of a loop, switch statement or labeled statement.
default Used to specify the default block of code in a switch statement.
deferred Used to load a library only when it is needed.
do Used to declare a loop that will iterate based on a condition.
dynamic Used to declare a variable without specifying a type.
else Used to specify a block of code to be executed, if the same condition is false.
enum Used to declare an enumerated (unchangeable) type.
export Used to export a library.
extends Used to specify a parent class.
extension Used to declare an extension method.
external Used to declare a function that is implemented externally.
factory Used to declare a factory method.
false Used to represent a Boolean false value.
final Used to declare a variable as final (read-only).
finally Used to specify a block of code to be executed, after a try/catch block, regardless of the result.
for Used to declare a loop that will iterate based on a condition.
Function Used to specify a function type.
get Used to declare a getter method or property.
print Used to print a message to the console.
throw Used to throw expcetions in a try/catch block.
true Used to represent a Boolean true value.
try Used to specify a block of code to be tested for errors.
typedef Used to declare a function type alias.
var Used to declare a variable.
void Used to declare a function that returns no value.
while Used to declare a loop that will iterate based on a condition.
with Used to specify a mixin.
yield Used to pause and resume a generator function.
yield* Used to delegate to another generator function.
import Used to import a library.
in Used to specify the iterable element in a for loop.
is Used to test if an object is a specific type.
library Used to specify a library name that will be used in the import statements.
future Used to specify a future type.
stream Used to specify a stream type.

These are the only few keywords but thre are more to explore. We will learn those slowly and understand them fully. Let’s dive a little deeper on some of the keywords.

asbtract in dart

asbtract keyword is used to declare a class as abstract. Abstract classes cannot be instantiated, but they can be subclassed. Abstract classes are useful for defining interfaces, often with some implementation.

Example

abstract class Vehicle {
  void start(); // Abstract method
  void stop(); // Abstract method
}

class Car extends Vehicle {
  @override
  void start() => print("Car started!");

  @override
  void stop() => print("Car stopped!");
}

class Bike extends Vehicle {
  @override
  void start() => print("Bike started!");

  @override
  void stop() => print("Bike stopped!");
}


void main() {  
  
  /// Accessing the class
  
  Car().start();
  Car().stop(); 
  
  Bike().start() ; 
  Car().stop() ; 

}

Output

Car started!
Car stopped!
Bike started!
Car stopped!

code Try Yourself

If you didn’t understand the code as of now, don’t worry. We will learn about classes in the upcoming lessons.You will understand the keywords use as we progress forward.

Quiz

Test your understanding!