Where to put your Angular models?
Before we go into detail - it's worth understanding what we mean by models:
- entity classes?
It could be all of them - depending on who you ask.
I personally like to differentiate between interfaces and models as two distinct things:
interfacesare used to define the shape of my Typescript entities
modelsare used as to define the actual value of my interfaces
How to organize your models in your Angular Project Structure
Every module may have a set of entities (models, enums, etc.) that are either private or public to the module itself.
Let's assume we have a module called
UsersModule. We want to define, for every entity, a sensible folder structure:
- users - components - services - enums - roles.enum.ts - interfaces - user.interface.ts - models
As you may have noticed, enums, interfaces and models all have their own folder, and it's important not to mix them to keep them well-organized.
There are a few rules that I tend to follow to make sure my project is well-organized.
Use a shared library for entities used outside of your modules
It's important to notice that a module should only contain the entities that are not shared with other modules, and hence that are private to that module.
But - Why?
Imagine we have a mono-repo with other applications or libraries written in different technologies (ex. Express, Stencil, React, etc.): you may not want to import your types from a different technology.
Create a separate library (for example, called
@enterprise/interfaces) that exposes your global entities. This is particularly recommended if you're using
Nx to structure your project.
Otherwise, consider creating a typescript repository to expose your global entities to different repositories.
Admittedly, this is not great - but if you have a large team of teams using the same interfaces, it could be really important to keep them in sync.
Never export an interface from a Service
This is a pattern that I quite dislike - and I see used very often.
Defining an interface within a Service (or a Component) is generally fine - although not something I normally do. It's all good - as long as it is not exported.
Why is that?
- A component should not import a service simply to get an Interface
- A component may simply use Typescript inference instead of using that Interface
- If the interface is reused and is used in a way that inference could not work, then it should defined in its own file
Hopefully this answered your questions - but if not, please do send me an email and I'd love to expand on the subject.
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