Dart Interview Questions and Answers for 5 years experience
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What is Dart and why is it used for Flutter development?
- Answer: Dart is a client-optimized programming language developed by Google. It's used for Flutter because it's fast, allows for hot reload (which significantly speeds up development), compiles to native code (resulting in performant apps), and is designed for building user interfaces with its rich set of widgets. Its garbage collection and asynchronous programming features make it well-suited for mobile development.
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Explain the difference between `const` and `final` keywords in Dart.
- Answer: Both `const` and `final` declare variables that cannot be reassigned after initialization. However, `const` implies a compile-time constant, meaning its value is known at compile time. `final` variables can be initialized at runtime. For example, `const x = 10;` is a compile-time constant, while `final y = DateTime.now();` is a `final` variable whose value is determined at runtime.
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What are isolates in Dart, and when would you use them?
- Answer: Isolates in Dart are independent workers that run in parallel. They have their own memory space and do not share memory with other isolates. This is crucial for avoiding race conditions and making Dart applications more responsive, especially when dealing with long-running or computationally intensive tasks. You'd use isolates for tasks like network requests, database operations, or complex calculations to prevent the UI from freezing.
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Explain the concept of Futures and Async/Await in Dart.
- Answer: Futures represent the eventual result of an asynchronous operation. They handle asynchronous programming in a more readable way than callbacks. `async` and `await` are keywords that make asynchronous code look and behave a bit more like synchronous code. `async` marks a function as asynchronous, allowing the use of `await` within it. `await` pauses execution until a Future completes and returns its value.
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What are Streams in Dart, and how do they differ from Futures?
- Answer: Streams are sequences of asynchronous events. Unlike Futures, which represent a single future value, Streams can emit multiple values over time. They are useful for handling continuous data flows like user input, network streams, or sensor data. Futures represent a single asynchronous operation's outcome, while Streams represent a sequence of asynchronous events.
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Describe different ways to handle errors in Dart.
- Answer: Dart uses `try-catch` blocks for error handling. `try` encloses the code that might throw an exception, `catch` handles exceptions of a specific type, and `finally` (optional) contains code that always executes, regardless of whether an exception was thrown. You can also use custom exceptions to handle specific error scenarios, and `on` clauses in `catch` blocks for more precise error handling.
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What are mixins in Dart, and how are they used?
- Answer: Mixins are a way to reuse code across multiple classes without using inheritance. They allow you to add functionality to a class without creating a subclass. Mixins are particularly useful for sharing common functionality between unrelated classes. You declare a mixin using the `mixin` keyword.
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Explain the concept of generics in Dart.
- Answer: Generics allow you to write type-safe code that can work with various data types without losing type information at compile time. This improves code reusability and reduces the risk of runtime type errors. You define generic types using angle brackets `
`, where `T` is a type parameter.
- Answer: Generics allow you to write type-safe code that can work with various data types without losing type information at compile time. This improves code reusability and reduces the risk of runtime type errors. You define generic types using angle brackets `
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