Explore creating robust HTTP services in Scala's functional programming paradigm. Gain insights into pure vs. impure implementations, their pros and cons, and effective tool usage.

scala-platform.tar.gz

Scala-Pure

Scala-Impure

Scala-Tapir

Scala-Impure-Test

Scala-Pure-Test

Scala-Tapir-Test

Test

Scala - Run Code Widget 

Scala-Pure-copy

Scala is one of the most popular general-purpose languages that supports both object-oriented and functional programming. In this course, you will learn how to create back-end HTTP services using Scala's functional programming paradigm.

You will also learn how to develop, test, and document the service using both pure and impure ways. You will be exposed to the differences between pure and impure implementation, their respective pros and cons, and how pure implementation can be more robust in terms of performance, understandability, testability, and type safeness. 

By the end of the course, you will have a clear idea of how functional programming works in Scala and how you can use the available tools more effectively.

Pure Functional HTTP APIs in Scala

# Update the pattern attribute in the documentation

Before you ask, we can update all parameters because we have only one.

(paths composeLens at("/product/{id}") composeOptional possible
    composeLens pathParams composeTraversal each composeOptional
    possible composeLens parameterSchema composeOptional possible
    composeLens schemaPattern)
        .set(Option("Fancy UUID regex here!"))(docs)

It seems that we can check off the first point on our list.

# Additional lenses for content schemas

We are left with modifying the pattern field of the actual model schemas. To get to these, we have to define some more lenses.

val components: Lens[OpenAPI, Option[Components]] =
  GenLens[OpenAPI](_.components)
//typeLens[Components, ListMap[String, OpenAPI.ReferenceOr[Schema]]]
val componentsSchemas =
  GenLens[Components](_.schemas)
//typeLens[Schema,ListMap[String,OpenAPI.ReferenceOr[Schema]]]
val schemaProperties =
  GenLens[Schema](_.properties)

The power of lenses allows us to traverse all of our structures and modify all affected models at once. So, we will use the functionality provided by the `Each` type class here. Let’s try something like the following code.

(paths composeTraversal each composeLens getOps).getAll(docs)

[error] ...: diverging implicit expansion for type cats.kernel.Order[A]
[error] starting with method catsKernelStdOrderForSortedSet in trait
        LowPrioritySortedSetInstancesBinCompat1
[error]     (paths composeTraversal each composeLens getOps).getAll(docs)
[error]                             ^            

This looks like an error from a binary incompatible Cats version. But this time, the compiler is lying to us.

We are missing another type class instance. This time, it is the one for `Each`, which we need to traverse our `ListMap` structure. So let’s write one!



Learn how to refine the generated documentation manually and explore the documentation.

Introduction

Impure Implementation

Pure Implementation

Testing Impure Services

Testing Pure Services

Benchmarks

Documentation

Epilogue

Refining the Generated Documentation: Part-II

Update the pattern attribute in the documentation

Additional lenses for content schemas