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Software Development Executive - II
Last updated on Oct 30, 2023
Last updated on Sep 21, 2023
Stepping into the world of software development, you soon stumble upon various design patterns which form the backbone of your coding structure. One such software design pattern prevalent in Dart and Flutter is the Dart Singleton! Let's talk about it!
The Singleton Pattern in Dart is a concept borrowed from the realm of Object-Oriented Programming (OOP). It falls under the Creational Design Pattern since it deals particularly with object-creation mechanisms, intending to provide a suitable object-creation blueprint.
The Dart Singleton, as the name suggests, is a singleton class that permits only one instance of itself to get created. This singleton instance provides a global point of access to it. In simpler terms, utilizing the singleton class, we restrict the instantiation of a class to a single instance that can be used across different classes in the Dart program.
This beneficial pattern entails that only one instance of a particular class is present in the Dart program. The class keeps track of its sole instance by saving it in a static variable. This single instance is called the singleton class, which is accessed via a single public static method.
Here's a simple approach to create a Dart Singleton,
1 class MySingleton { 2 3 // Private constructor 4 MySingleton._privateConstructor(); 5 6 // Static final instance 7 static final MySingleton _instance = MySingleton._privateConstructor(); 8 9 // Static method 10 static MySingleton get instance { 11 return _instance; 12 } 13 } 14
In the code snippet above, the singleton class MySingleton is created with a private constructor and a static final singleton instance of the same class. The static method get instance is the global access point for the MySingleton instance.
One of the powerhouse advantages of implementing a Dart Singleton is the control over resource consumption. Often, creating many instances consumes a lot of resources, pressing a need for a design pattern where only one instance is created, and the same instance is shared with every class requesting it.
With the Singleton Pattern, every repeated call will return the same instance, thus aligning with instance conservation and resource optimization.
Now that we have a solid understanding of the Singleton Pattern, let's apply this to the Dart programming language. Dart offers exciting features that allow the creation of Singleton classes in different ways. The two primary methods are through the 'default constructor' and the 'factory constructor.'
In Dart, Singleton can be created by making the constructor private. A private constructor guarantees that a new instance of the same class can't be created from outside the class. This would mean that an external class can't create an instance of this singleton class. To overcome this hurdle, Dart uses a static instance of this class to be created at the time of class loading, which is returned by a factory method.
1 class FirebaseAuthRepository { 2 FirebaseAuthRepository._privateConstructor(); 3 4 static final FirebaseAuthRepository _instance = FirebaseAuthRepository._privateConstructor(); 5 6 factory FirebaseAuthRepository() { 7 return _instance; 8 } 9 } 10
The privateConstructor() is the private constructor, and instance is the static, final instance of the class. The factory method FirebaseAuthRepository() returns this static final all-new instance. This is the first step towards creating and using Dart Singleton.
Another interesting way of creating a class Singleton in Dart would be using a factory constructor. With Dart's factory keyword, if you return an existing instance of a class, it transforms the constructor into a factory constructor.
1 class MySingleton { 2 static MySingleton _singleton; 3 4 factory MySingleton() { 5 if (_singleton == null) { 6 _singleton = MySingleton._internal(); 7 } 8 return _singleton; 9 } 10 11 MySingleton._internal(); 12 } 13
In this factory constructor approach, the factory keyword preceding the constructor allows returning an instance of a class. Using factory constructors, we gain the ability to instantiate a singleton pattern that ensures only one instance of the class is created.
This duality of Dart Singleton creation applies a versatile edge to Singleton classes, bringing flexible Singleton objects within the context of different Flutter apps.
After getting a grasp of Dart Singleton and its implementation, let's move ahead and discuss some advanced concepts and their importance in Dart.
An interesting aspect of Singleton in Dart includes the Lazy Singleton Pattern. Lazy Initialization, also known as lazy loading, is a process in which an object is not initialized until it is required. This is particularly beneficial in circumstances where object creation is a heavy process that consumes memory resources, even when it's not in immediate use. Dart Singleton supports Lazy initialization.
1 class Singleton { 2 static Singleton _singleton; 3 4 Singleton._internal(); 5 6 static Singleton get instance { 7 if (_singleton == null) { 8 _singleton = Singleton._internal(); 9 } 10 return _singleton; 11 } 12 } 13
In this code snippet, the instance of Singleton is not created until it gets called by the static getter 'instance.' If this instance does not exist, it's created and returned - ensuring lazy initialization.
While working with multithreaded languages like Dart, Singleton classes might confront challenges. For instance, if two threads are simultaneously trying to access a singleton object, there's a potential threat of creating more than one instance. Dart, being single-threaded, minimizes this peril, and the Singleton pattern can be implemented smoothly.
This pattern ensures a class only has one instance and provides a global point of access to it. Despite the nuances in the implementation, the key objective remains to return the same instance regardless of how and where you access it.
Now, let's take a quick look at how the Singleton pattern plays a vital role when developing applications using Flutter. The Singleton pattern is heavily used in Flutter predominantly to solve problems related to State Management.
The Singleton pattern is crucial not only for managing global variables but also for managing state in a Flutter app. With ever-evolving application scale, the need for a unified state that is not only shared but is also accessible throughout the entire app code becomes essential. Here, Singleton swoops in as a savior.
Let's consider an instance where a Flutter app belongs to a class FirebaseAuthRepository. The repository is to be used across the app to handle user authentication. Here, we could implement the Singleton pattern like so:
1 class FirebaseAuthRepository { 2 FirebaseAuthRepository._privateConstructor(); 3 4 static final FirebaseAuthRepository instance = FirebaseAuthRepository._privateConstructor(); 5 6 void signIn(String password) { 7 // A simple functionality example 8 } 9 } 10 11 // Using the Singleton in the application code 12 void main() { 13 FirebaseAuthRepository.instance.signIn('password'); 14 } 15
Above, the FirebaseAuthRepository class uses the singleton pattern to ensure that we only ever have one instance of it, which we access using 'instance.' We've also included a method called 'signIn' as a simple instance of functionality, and the Singleton instance is used in the main() function.
Even though Dart is single-threaded, it uses asynchronous operations like Futures and Streams. Furthermore, Dart also supports multi-threading using Isolates, and each Isolate has its heap space, which means if you create a Singleton instance, that instance is not shared between different Isolates. This prompts the creation of separate isolates within a singleton design pattern to manage threads efficiently.
With such a flexible toolkit, implementing the singleton pattern in Flutter can greatly organize and streamline your application code.
Having explored the depths of the Dart Singleton, we conclude it's far more than just a standard design pattern. It is a set of practices that transform your Flutter development journey and enhance the efficiency of the application on the whole.
For instance, think of Singleton classes as a single window manager in an operating system. This window manager controls all open windows in the operating system, where directly creating more than one instance of the manager would lead to chaos! Hence the singleton pattern ensures that only one manager exists, thereby maintaining harmony within the system!
Singletons have a key role in Flutter, especially while dealing with different plugins, those as Firebase. Being connected with all the Firebase plugins, the necessity of keeping global variables or instances increases. Singleton Classes in Dart, thus, aids in seamless state management across an extensive Flutter app.
One must not ignore the role of Dart Singleton when addressing Dependency Injection in Dart, an essential practice while working on bigger projects. This primarily relates to the Object-Oriented Programming paradigm, where objects provide dependencies to other objects. With Singleton Classes in Dart, you find yourself with smart and smooth Dart code with effective dependency injection.
The Dart Singleton pattern, thus, doubles up as a globally accessible object and a state manager ensuring a highly efficient memory usage. It's not only about providing a suitable object creation mechanism but also centres around giving that object global access points.
To sum up, Dart Singleton might just be the secret ingredient to your next Flutter masterpiece. With efficient memory management and smoother state control, embark on a journey of creating complex yet efficient Flutter applications with Dart Singleton.
Leverage Dart Singleton to its fullest and let every Flutter app of yours stand testament to the power of smart coding!
With this, we wrap our whirlwind tour of Dart Singleton. As a Flutter developer, understanding, and effectively using Dart Singleton can greatly enhance your coding prowess, pushing you up a notch on the developer ladder. So get practising and write power-packed codes with Dart Singleton. Happy Coding!
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