Summary

As long as we're working within Reason, the type system will prevent you from running into runtime type errors. However, when interacting with the outside world—whether it be JavaScript or external data—we lose those guarantees. To be able to preserve these guarantees within Reason's boundaries, we need to help out the type system when using things outside Reason. We previously learned how to use external JavaScript in Reason, and in this chapter we've learned how to use external data in Reason. Although writing decoders and encoders is more challenging, it's quite similar to writing JavaScript bindings. In the end, we're simply telling Reason the type of something external to Reason. With GraphQL, we can extend the boundaries of Reason to include external data. There are trade-offs, and nothing is perfect, but it's definitely...