Use Python package enum type in JavaScript app

This article provides an introduction to cross-technology handling of enum type. In programming, an enum (short for enumeration) type is a special data type that enables for a variable to be a set of predefined constants. The variable must be equal to one of the values that have been predefined for it. Enums are used to create our own data types, just like classes. They are particularly useful when we want to represent a fixed set of constants, such as days of the week, states, colors, directions, and more. This makes the code more readable and less prone to errors.

Javonet allows you to reference and use modules or packages written in (Java/Kotlin/Groovy/Clojure, C#/VB.NET, Ruby, Perl, Python, JavaScript/TypeScript) like they were created in your technology. If have not yet created your first project check Javonet overview and quick start guides for your technology.

With Javonet, you can interact with enum types from Python package as if they were available in JavaScript, but interaction must be performed through the Javonet SDK API. This allows you to handle and manipulate enum values, pass them to methods, and return them from methods, all while maintaining the type safety and readability of your JavaScript code.

Custom Python package with enum type

With Javonet it is possible to reference any custom Python package and interact with its methods declared on types defined within that module almost the same as with any other JavaScript library.

Snippet below represents the sample code from Python package which contains enum type. 

from enum import Enum
class Fruit(Enum):
    Apple = 1
    Banana = 2
    Orange = 3
    Mango = 4

Fruits = []

@staticmethod
def add_fruits_to_list(fruits):
    TestClass.Fruits.extend(fruits)
    return "{0} fruits on the list".format(len(TestClass.Fruits))

Javonet SDK contains various methods to interact with enums and consume the results in JavaScript:

I code in:
// use Activate only once in your app
Javonet.activate("your-license-key")

// create called runtime context
let calledRuntime = Javonet.inMemory().python()

// set up variables
const libraryPath = resourcesDirectory
const className = "TestClass.TestClass"

// load custom library
calledRuntime.loadLibrary(libraryPath)

// get type from the runtime
let calledRuntimeType = calledRuntime.getType(className).execute()

// create enum items
let fruit1 = calledRuntime.getEnumItem(calledRuntimeType, "Fruit", "Mango");
let fruit2 = calledRuntime.getEnumItem(calledRuntimeType, "Fruit", "Orange");

let fruit1Name = fruit1.getEnumName().execute().getValue()
let fruit2Name = fruit2.getEnumName().execute().getValue()
let fruit1Value = fruit1.getEnumValue().execute().getValue()
let fruit2Value = fruit2.getEnumValue().execute().getValue()

// write result to console
console.log("%s: %d, %s: %d", fruit1Name, fruit1Value, fruit2Name, fruit2Value)

This snippet uses in memory runtime bridging to load the Python package and next retrieves reference to specific enum type. Then two enum items are created. Their values and names are checked.

Enum items can be passed to Python package method:

I code in:
// use Activate only once in your app
Javonet.activate("your-license-key")

// create called runtime context
let calledRuntime = Javonet.inMemory().python()

// set up variables
const libraryPath = resourcesDirectory
const className = "TestClass.TestClass"

// load custom library
calledRuntime.loadLibrary(libraryPath)

// get type from the runtime
let calledRuntimeType = calledRuntime.getType(className).execute()

// create enum items
let apple = calledRuntime.getEnumItem(calledRuntimeType, "Fruit", "Apple");
let mango = calledRuntime.getEnumItem(calledRuntimeType, "Fruit", "Mango");

// create fruits array
let fruits = [apple, mango]

// invoke type's static method
let response = calledRuntimeType.invokeStaticMethod("add_fruits_to_list",
    fruits).execute()

// get value from response
let result = response.getValue()

// write result to console
console.log(result)

In this example, two enum items are created, too. Then array of enums is created and passed to method which adds enum items to list.

The same operation can be performed remotely by just changing the new Runtime Context invocation from in memory to tcp that will create and interact with your Python package objects on any remote node, container or service that hosts Javonet Code Gateway. This way you can preserve the same logic in your application and instantly switch between monolithic and microservices architecture without the need to implement the integration layer based on web services or other remote invocation methods.

Read more about use cases and software architecture scenarios where Javonet runtime bridging technology can support your development process.