Scripting

Most of a flow is configured, not coded. When a step needs logic no plugin offers - a calculation, a rule, a format of your own - put a script component there and write that step in C#, Python or JavaScript. The rest of the flow stays visual.

How a script component works

A script component receives each record on its Input pin, runs your code, and sends records on with Next. Your code gets three things:

• the record, as an object of its flow type with real properties (inputData.Email),
• the metadata of the message, which you pass on with the records you send,
• the flow services (Services in C#, services in Python and JavaScript): logging, settings, storage, assets, batches and more, under the same names in all three languages. See Flow services.

Call Next once to pass one record on, several times to split a record into many, or not at all to drop it. When the component's Output has no connection, pass the input on. Every flow type is available as a class, so you create output records with new CustomerDto() (C#, JavaScript) or CustomerDto() (Python).

An exception stops the record and goes to the flow's error handling, like an error in any other component.

Choose a language

	C#	Python	JavaScript
Runs as	Compiled into the flow's assembly	CPython 3.11+ embedded in the host	V8 embedded in the host
Speed	Fastest; compiled code	Interpreted	JIT-compiled
Libraries	NuGet packages added to the flow	pip packages installed in the host's Python	Built-ins, fetch, timers; no modules
Messages	In parallel (or one instance per message)	One at a time per component	One at a time per component
Editor	Completion, hover and live compile errors	Syntax highlighting; full completion in your own IDE with the viaducta package	Syntax check
Debugger	Breakpoints and stepping	Line tracing with local variables	Breakpoints, stepping, variables

Use C# for throughput and for anything that needs .NET libraries. Use Python when your team writes Python or needs a Python package. Use JavaScript for light transformations and HTTP calls with fetch.

Pages

• C# script, with the C# shared script for code used by several components.
• Python script.
• JavaScript script.
• Decision conditions: route records with a C# condition.
• Pre-execution scripts: change a component's configuration for each message.
• Flow services: everything Services offers.
• Cookbook: short recipes in all three languages.