Flutter keywords should learn them

Overview

Dart/Flutter has many keywords that define the language's structure. Here are the most important ones to know for interviews and development.

Variable & Type Keywords

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var       // Type inferred from value
final     // Set once, value known at runtime
const     // Compile-time constant
dynamic   // No type safety — runtime typed
late      // Initialize later (non-null)
Object    // Base of all Dart objects
void      // No return value
Null      // Null type

// Examples
var name = 'Alice';
final age = 28;
const pi = 3.14159;
dynamic anything = 42;
late String lazyValue; // Initialize before use

Class & OOP Keywords

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class       // Define a class
abstract    // Cannot be instantiated directly
extends     // Inherit from parent class
implements  // Implement an interface (all methods required)
with        // Use a mixin
mixin       // Define a mixin (reusable code without inheritance)
super       // Access parent class members
this        // Reference current instance
static      // Class-level (not instance)
override    // Mark method as overriding parent
sealed      // All subclasses must be in same file (Dart 3+)

class Dog extends Animal with Loggable implements Trainable {
  @override
  void speak() => print('Woof');
}

Control Flow Keywords

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if / else
for / while / do-while
switch / case / default
break / continue
return
// Dart 3+: pattern matching in switch
switch (shape) {
  case Circle(radius: final r) => print(r);
}

Async Keywords

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async     // Marks function as async
await     // Wait for Future to complete
sync*     // Synchronous generator (Iterable)
async*    // Asynchronous generator (Stream)
yield     // Emit value from generator
yield*    // Yield all values from another iterable/stream

Future<String> fetchData() async {
  final response = await http.get(url);
  return response.body;
}

Error Handling

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try / catch / finally / on / rethrow / throw

try {
  await fetchData();
} on SocketException catch (e) {
  print('No internet: $e');
} catch (e, stack) {
  print('Error: $e');
} finally {
  cleanup();
}

Other Important Keywords

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import    // Import a library
export    // Re-export from a file
library   // Declare library name
part / part of // Split library across files
typedef   // Create function type alias
enum      // Enumeration
extension // Add methods to existing types
factory   // Constructor that returns instance (can return subtype/cache)
operator  // Override operators (+, ==, [], etc.)
is / as / is! // Type check and cast
in        // Used in for-in loops
new       // (Optional) create instance — rarely used in modern Dart

Key Flutter-Specific Annotations

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@override
@required     // (older code — now just 'required' keyword)
@deprecated
@protected
@immutable
@visibleForTesting

Must-know for interviews:

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var

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final

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const

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dynamic

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late

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async/await

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abstract

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extends

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implements

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with

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mixin

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factory

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sealed

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typedef

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extension

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