Domain Modeling Made Functional

Using bind and map in Our Pipeline

We understand the concepts now, so let’s put them into practice. We’ll compose the workflow pipeline using our error-generating functions, tweaking them as necessary so that they fit together.

Let’s quickly revisit the components of our pipeline, focusing on Result and ignoring the Async effect and the service dependencies for now.

First, ValidateOrder will return an error if the input data is not in the right format, so it’s a “switch” function and its signature will be like this:

type ValidateOrder =
  // ignoring additional dependencies for now
  UnvalidatedOrder                             // input
    -> Result<ValidatedOrder, ValidationError> // output

The PriceOrder step may also fail for a variety of reasons, so its signature ...