How to Handle Singleton Injection with Parameter in Flutter Using Get_it and Injectable

Discover effective ways to manage singleton injection with parameters in Flutter, particularly for setting different base URLs for app flavors using Get_it and Injectable.
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Handling Singleton Injection with Parameter in Flutter

When developing Flutter applications, managing dependencies efficiently is crucial for writing clean and maintainable code. One challenge that developers often encounter is how to deal with singleton injections that require parameters, especially when needing different base URLs for various app flavors. In this post, we'll explore a solution using the powerful packages get_it and injectable. Let's dive into this common issue and how to solve it effectively.

The Problem

In a typical setup with singleton instances, you might want to initialize these instances with different parameters. For example, if your application has different flavors (development, staging, production), it's common to have different base URLs for these environments. However, using @ factoryParam in injectable is unsuitable since it is designed for factory methods, not for singletons.

The Challenge

Here’s a breakdown of the challenge you might be facing:

Singleton Requirement: You need to keep your instances as singletons for consistency throughout the app.

Parameterized Constructor: You want to pass a base URL as a parameter to the constructor.

Limitations of @ Injectable: The injectable package provides an annotation @ factoryParam, but it does not support singleton injection directly.

The Solution

Fortunately, there are effective patterns to tackle this issue. Here are two primary approaches you can take:

Approach 1: Environment-based Registration

One practical method is to register different strings as environment variables. This allows you to define specific URLs for different environments. Here’s how to do it:

Step 1: Define the Environments

You can define separate base URLs for each environment using the @ Environment annotation:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Create Singleton Classes

Now, you can create singleton classes that utilize the base URL dynamically depending on the environment. For example:

[[See Video to Reveal this Text or Code Snippet]]

Approach 2: Using a Single Class with Named Parameter

If you prefer a simpler approach, you can consolidate all logic into a single class using the same @ Named parameter:

[[See Video to Reveal this Text or Code Snippet]]

This solution maintains the singleton pattern while still allowing you to inject the desired base URL based on the environment.

Conclusion

Using either approach provided above, you can effectively manage singleton injection with parameters in Flutter using get_it and injectable. Understanding how to register different configurations based on environments can streamline your development process, ensuring your application works seamlessly with multiple flavors. Whether you choose to implement environment-based registration or utilize a single class approach, both methods have their merits. Choose the one that best fits your project’s requirements and structure.

By managing your dependencies wisely, not only do you keep your code clean, but you also ensure greater flexibility in handling variations in app environments, making it a valuable skill in your Flutter toolbox.