Understanding and Applying FutureOr with Examples

Introduction: Dart and FutureOr<T>

Dart is a platform-independent programming language developed by Google for web, server, and mobile application development. In this post, we will introduce and explore Dart's special type, FutureOr<T>, through explanations and examples.

Asynchronous programming is essential in modern web development, and Dart brings many benefits to this field. In Dart, asynchronous tasks are handled using a Future object. In addition, Dart provides a FutureOr<T> type that allows you to express and handle the result of an asynchronous operation, which may consist of an uncompleted Future or a completed value.

In this post, we will cover the following topics:

• Definition and principles of FutureOr<T>
• Practical use cases and examples of FutureOr<T>
• Conclusion and closing remarks

Now, let's embark on our journey to explore Dart's FutureOr<T>.

Definition and Principles of FutureOr<T>

First and foremost, FutureOr<T> in Dart's type system signifies 'a task that can produce a value of type T (either a Future containing a T value or a directly held value with T as its type)'. By using this expression, asynchronous tasks with results that can be either a Future or a T can be managed flexibly.

FutureOr<T> is useful in the following situations:

• When synchronous and asynchronous tasks are mixed
• When a single function or method returns both synchronous and asynchronous tasks
• When execution needs to be paused or waited until the completion of an asynchronous task

To help with understanding, let's look at the code example below:

import 'dart:async';

FutureOr<int> getValue() async {
  return await Future.delayed(Duration(seconds: 1), () => 10);
}

void main() async {
  final value = await getValue();
  print('Value is: ' + value.toString());
}

In the example above, the getValue function returns a FutureOr<int> type. The return value can be awaited for the asynchronous result using await. In this case, 'Value is: 10' is printed.

By specifying the type as FutureOr<T>, synchronous and asynchronous values can be delivered through a consistent interface. This is the principle behind FutureOr<T>.

In the next section, we will examine specific examples and use cases leveraging this principle.

Practical Use Cases and Examples of FutureOr<T>

Now, let's delve into the use cases and examples of FutureOr<T>. The following example demonstrates how to handle synchronous and asynchronous operations with a single interface using FutureOr<T>.

import 'dart:async';

FutureOr<String> fetchData(bool fromServer) async {
  if (fromServer) {
    return await Future.delayed(Duration(seconds: 1), () => 'Data from server');
  } else {
    return 'Data from cache';
  }
}

void main() async {
  final serverData = await fetchData(true);
  print(serverData);

  final cacheData = await fetchData(false);
  print(cacheData);
}

In the code example above, the fetchData function takes a bool type parameter, simulating fetching data from a server when true, and fetching data from cache when false. The type of the function return value is FutureOr<String>.

When fetching data from a server, the operation is asynchronous, obtaining the value after 1 second, while fetching data from the cache is handled synchronously. In this way, both synchronous and asynchronous operations can be managed simultaneously.

import 'dart:async';

FutureOr<int> multiply(int a, int b) {
  return a * b;
}

FutureOr<String> getResult(int result) async {
  return await Future.delayed(Duration(seconds: 1), () => 'Result: $result');
}

void main() async {
  final value = await getResult(multiply(5, 2));
  print(value.toString()); // Output: Result: 10
}

In the code example above, the multiply function multiplies two integer values and returns a result, which is processed synchronously. The getResult function then handles the received result asynchronously, converting it into a string. Here, the flexibility of FutureOr<T> can also be utilized.

Through such examples, we have verified that FutureOr<T> can effectively manage synchronous and asynchronous tasks with a consistent interface. In the next section, we will proceed with the conclusion and closing remarks.

Conclusion and Closing Remarks

In this post, we have explored the FutureOr<T> in the Dart programming language. FutureOr<T> is a flexible type that allows for handling both synchronous and asynchronous operations with a single interface, greatly benefiting modern web programming. We have covered the following topics:

• Definition and principles of FutureOr<T>
• Practical use cases and examples of FutureOr<T>

Through this, we have gained an understanding of the basic concepts and application methods of FutureOr<T>. Now, we can efficiently manage synchronous and asynchronous tasks using the Dart language, and develop web, server, and mobile applications accordingly.

Lastly, it is important to accurately grasp and skillfully apply these concepts through continuous learning and practice. We hope you build successful coding experiences in various real-world projects.

Thank you.