Kotlin programming model

Cloud Functions provides two Kotlin programming models: one is based on top-level functions, the other, on the YcFunction interface. Unlike top-level functions, the YcFunction interface enables you to access the invocation context.

Both programming models enable using Yandex Cloud services via the SDK. To do this, add the SDK to the Gradle dependencies.

Distinct data typesDistinct data types

Kotlin programming models feature various distinct data types, such as InputStream, String, and ByteArray. They are used differently from other types. If the handler argument is of a distinct type, the runtime does not convert an incoming HTTPS request to JSON. Instead, it sends the request directly to the user handler.

Handling distinct types is different when they become Nullable. Let’s assume the request body is null and the user invokes the function with the ?integration=raw parameter. The result the handler gets depends on the argument type:

• If the argument is String?, the handler gets the null value.
• If the argument is String, the handler gets a string containing the null text.

Handler requirementsHandler requirements

No matter which model you select, the project can be uploaded as source code, a JAR archive, or a Gradle project. The requirements applied to handler classes also depend on the programming model:

• For top-level functions:

  • The function must be public.
  • It must not be generic.

• For the YcFunction interface:

  • The handler class must be public.

  • It must have a public no-argument constructor.

    It is provided by default. However, if you created your own constructor with arguments, you should also create a no-argument one.

  • The class must not be generic.