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Discover effective solutions for generating a `circular library` in Angular with step-by-step guidance to eliminate dependency conflicts.
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Understanding the Circular Library Problem in Angular

Creating libraries in Angular can sometimes lead to complex issues, particularly when dealing with circular dependencies. A circular dependency occurs when two or more modules rely on each other, creating a loop in the code that can confuse the Angular compiler and ultimately cause build errors.

This guide addresses a common scenario: generating a circular library with two libraries (@ core/entity and @ core/model) where classes within them depend on each other (e.g., UserEntity depending on OrganizationModel and vice versa). We will explore why these errors occur and how to effectively resolve them.

The Circular Dependency Scenario

The Libraries Involved:

Entity Library: @ core/entity

Contains:

UserEntity

OrganizationEntity

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

Model Library: @ core/model

Contains:

UserModel

OrganizationModel

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

The Problem

When you attempt to build your entity library, Angular often removes the classes from the dist directory due to the circular dependency. As stated, since UserEntity imports OrganizationModel, and OrganizationModel in turn imports OrganizationEntity, this creates a loop that Angular cannot resolve, resulting in errors indicating that certain classes do not exist.



Solutions to Resolve Circular Dependencies in Angular

Let’s explore some potential solutions to fix this issue effectively:

1. Use a Third Library for Shared Interfaces

One quick approach to eliminate circular dependencies is to create a third library that both libraries can reference. This new library can hold shared interfaces or common classes:

Step 1: Create a new library (let’s call it @ core/shared).

Step 2: Move common interfaces used by both UserEntity and OrganizationModel into this shared library.

Step 3: Reference these shared interfaces in both @ core/entity and @ core/model libraries instead of directly depending on each other.

Advantages

This approach minimizes direct dependencies and makes libraries more modular and reusable.

2. Replace Class Dependencies with Interfaces

If your entity classes primarily hold data, consider using interfaces instead of classes.

Example Change:

You can replace OrganizationModel in UserEntity with an interface:

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

Advantages

Using interfaces reduces the overhead of class dependencies, as interfaces do not get compiled to JavaScript code, thus avoiding potential circular references.

3. Simplify Your Structure

Another approach is to review and simplify your library structure. Ask yourself:

Is it necessary for UserEntity to reference OrganizationModel?

Are there alternative designs that avoid the need for circular dependencies altogether?

By simplifying and restructuring your code, you may eliminate the circular dependency naturally.



Conclusion

Circular dependencies can be a daunting challenge when developing libraries in Angular, but they can often be resolved using strategies such as creating a shared library, utilizing interfaces, or restructuring the architecture. By applying these methods, you can ensure that your Angular projects are well-organized and free from dependency-related issues.

If you find yourself facing this problem, consider implementing the solutions we've discussed. Good luck with your Angular projects!