InversifyJS VS reflect-metadata

Take a class for which we are tasked to write a unit test. This class may have a dozen methods and a dozen more attributes. In my environment we were already using inversify to dependency inject into this class, and using container snapshot and restore as setup and teardown operators, in our jest test file. But it began getting out of control even after refactoring into test cases and test runners.

Inversify (https://inversify.io/) for IoC.

Alguns frameworks trabalham desta forma por padrão, como é o caso do Angular, quando este não é o padrão do framework que utilizamos podemos usar alguma biblioteca, como a Inversify ou tsyringe da Microsoft.

Using decorators required setting an --experimentalDecorators experimental compiler flag. Several popular TypeScript libraries, such as type-graphql and inversify, rely on this implementation.

inversify

It blows 🤯 my mind to think that my #opensource project InversifyJS has reached over 100 MILLION DOWNLOADS on npm. InversifyJS is a lightweight (<50KB) but powerful Inversion Of Control (IoC) container for #JavaScript applications powered by #TypeScript. It is used to implement Dependency Injection (DI) in thousands of applications, including high-profile products like Microsoft Sway and over forty thousand open source repositories on #GitHub and over two thousand open source packages on #npm.

we use https://inversify.io/ in production, it works great.

Counter to this post, as soon as I read the title I knew what this was, & I knew it was speaking exactly to something we've wanted for a long time. This is asking for more official & better supported https://github.com/rbuckton/reflect-metadata .

TypeScript is a compiler. It has a lot of type information during compilation. We could write that type information out into a file. Instead what we do is throw that information out when the compile ends. Taking all that typing information & throwing it away at the end of compile time is a bad dumb & silly limitation. Especially for a language like JavaScript, which historically could be semi-proud it had such a strong Everything Is An Object philosophy running through it (such as the malleable prototype-based inheritance system); so much type information should be on that Class object. Reflect-metadata for example defined new methods on Reflect to store this metadata.

I could not be more delighted to see the pennon of this website go up. We needed a rallying point for this. We needed a rallying point for keeping class data around. A rallying point for enriching the runtime with good actionable data is a good rallying point.

It's not what's afoot here, but I think you're a bit off-base about the impossibility of adding even some type-safety. We might not be able to get exact TS type safety. But we can definitely build some safety in. Owing to the malleable prototype-based type system in JS, we can add getters/setters to objects to do a lot of type checking. This doesn't even begin to explore the possibility of what we might do with es2015's proxies, which could allow even more interesting checks to be layered in. I also wish JS had an official AST (and renderer), so had more official options for code-rewriting that might let us weave in type checks.

What we can do as programmers is limited by what we have at our disposal. Not throwing out all the typing information, keeping it around at runtime, opens a lot of interesting doors.

Second, TypeScript 5.0 cannot emit decorator metadata. Subsequently, it doesn’t integrate with the Reflect API and won’t work with the reflect-metadata npm package.

Database columns will be mapped to domain object properties using decorators. This will include relationships and enum types. reflect-metadata stores metadata about the classes and properties. Most of the work is a simple map for each class, renaming db column properties to domain model properties and vice versa. Reflect.defineProperty holds a list of field metadata on the target class. This is where more database ORM logic could live in the future such as column type, length, etc. A base domain model entity will use this metadata to map the models appropriately.