Top 30 Dart Programming Interview Questions & Answers

The main() function is the entry point of a Dart application. It is the first function that gets executed when the program starts running.

Dart is known for its features such as a strong static type system, efficient just-in-time (JIT) and ahead-of-time (AOT) compilation, asynchronous programming support, and a rich set of libraries.

var: Dynamically typed variable, its type is inferred at runtime. 
final: Can be assigned only once and its value is known at runtime. 
const: Compile-time constant with a constant value that must be known at compile time.

async and await are used for asynchronous programming. async is used to declare a function as asynchronous, and await is used to wait for the result of an asynchronous operation.

“is” is used for type checking, returning true if the object is of the specified type. “as” is used for type casting, allowing you to treat an object as an instance of a different type.

The pub is the Dart programming language’s package manager, with reusable libraries and packages for Flutter, AngularDart, and standard Dart apps. Some fundamental commands: To get dependencies, use pub get. To upgrade a dependency, use pub upgrade.

Strings: String values are represented by the keyword String. 
Booleans: A Boolean value is represented by the bool keyword. 
Lists: Predefined List classes are used to describe lists. 
Maps: Predefined Map classes are used to describe Maps. 
The Dynamic Type: The dynamic keyword is explicitly used as a type annotation.

Dart’s sound null safety is a feature that helps catch null-related errors during development. It introduces non-nullable types and promotes safer and more predictable code by providing compile-time guarantees against null reference errors.

JIT (Just-In-Time) compilation in Dart occurs at runtime, translating code into machine language as the program runs. AOT (Ahead-of-Time) compilation, on the other hand, happens before runtime, translating code into machine language during the build process. AOT compilation is typically used for producing more efficient and faster-executing code.

Dart uses asynchronous programming to handle tasks that might take some time to complete without blocking the program’s execution. The async/await pattern simplifies asynchronous code, making it more readable and maintainable. It allows developers to write asynchronous code in a style similar to synchronous code, improving code structure and comprehension.

The covariant keyword in Dart is used to allow a subclass to override a method with a more specific type. It is often used when dealing with method parameter types in a class hierarchy, allowing a subclass to narrow down the type of a parameter compared to its superclass.

Flutter uses Dart as its primary programming language to build cross-platform mobile applications. Dart’s hot-reload feature and reactive framework make it well-suited for Flutter development. The advantage of Flutter is its single codebase for both iOS and Android, providing a consistent and efficient development experience.
Furthermore, the `pubspec.yaml` file defines assets like images, fonts, and other resources, ensuring they are bundled with the application. This centralized configuration guarantees consistency across development environments and ensures that the correct packages and resources are incorporated into the final app, making it an essential component of every Flutter project.

Lazy loading in Dart, achieved using the deferred keyword, allows parts of the code to be loaded on-demand, reducing the initial load time of an application. This is especially important for larger applications where loading all code upfront might lead to slower startup times.

In Dart, reflection can be achieved without using the dart:mirrors library through code generation tools like source_gen. By annotating classes or methods and using code generation, developers can achieve similar reflective capabilities without the runtime overhead of dart:mirrors.

Zones in Dart are used to encapsulate and manage asynchronous code execution. They provide a way to set up error handlers and manage the flow of asynchronous operations. A practical use case is in web applications, where different parts of the code may need to handle errors or side effects differently, and zones help manage these contexts.

Dart uses a garbage collector to automatically reclaim memory that is no longer in use. The garbage collector identifies and frees up memory occupied by objects that are no longer reachable.

Mixins are a way to reuse a class’s code in multiple class hierarchies. A mixin is a class that provides methods that can be used by other classes without the need for inheritance.

Futures represent values or errors that will be available at some time in the future. They are used for asynchronous programming to handle computations that may take some time to complete.

Dart uses try, catch, and finally blocks for error handling. Exceptions are thrown using the throw keyword and caught using the catch block.

Streams are a sequence of asynchronous events. They are used for handling a series of data, where each piece of data is processed asynchronously.

The super keyword is used to refer to the superclass and access its methods or properties in the context of a subclass.

Code splitting in Dart can be achieved using the deferred keyword, allowing parts of the code to be loaded on-demand rather than all at once.

Named constructors are special constructors with names. They provide a way to create multiple constructors for a class, each with a different name.

The .. cascade operator allows you to perform a sequence of operations on the same object, without having to repeat the object reference.

The with keyword is used to implement mixins in Dart. It is followed by one or more mixin classes in a class declaration.

Dart uses the ? operator for null-aware operations. For example, int? a = null; declares a nullable integer variable.

Isolates are Dart’s concurrency model for handling parallelism. They are independent workers that communicate by passing messages.

The async* keyword is used to define asynchronous generators, which allow you to generate a sequence of values asynchronously.

Dart supports reflection through the dart:mirrors library, allowing you to inspect and manipulate objects at runtime.

The typedef keyword is used to create a function type alias, providing a way to define a type for a function.