Functions

Function artifacts encapsulate reusable logic that can be called from any integration artifact. By default, every function is added to the functions.bal file in the project root.

Adding a function

Visual Designer

1. Click + next to Functions in the sidebar. Alternatively, click + Add Artifact in the Design panel, then click Function under Other Artifacts or Library Artifacts.

   

2. Fill in the Create New Function form.

   

   Field	Description
   Name	A unique identifier for the function (for example, validateOrder). Required.
   Description	Optional description of the function's purpose.
   Public	Select Make visible across the project to allow use from other integrations.
   Parameters	Click + Add Parameter to define each input. Each parameter requires a name and a type, and optionally a description.
   Return Type	The type of the value returned by the function. Leave empty for functions that return nothing.

3. Click Create. The function is added to functions.bal and opens in the flow designer canvas, where you add the integration steps as the function body.

Ballerina Code

import ballerina/lang.regexp;

# Validates an email address
# + email - The email address to validate
# + return - Whether the email address is valid
public function isValidEmailAddress(string email) returns boolean {
    string:RegExp|error emailPattern = regexp:fromString("^[a-zA-Z0-9._%+\\-]+@[a-zA-Z0-9.\\-]+\\.[a-zA-Z]{2,}$");
    if emailPattern is error {
        return false;
    }
    return emailPattern.isFullMatch(email);
}

Editing a function

To open and edit a function's flow view, click its name in the sidebar under Functions.

To change the function's name, description, parameters, or return type, click Configure in the top-right of the flow view.

Project organization

By default, all functions are added to a single functions.bal file at the project root. For larger projects, you can split functions into additional .bal files grouped by domain.

my-integration/
├── functions.bal              # Default file for all functions
├── types.bal
├── connections.bal
└── main.bal

To split functions across multiple files, create new .bal files at the project root and move related functions into them.

my-integration/
├── functions.bal              # General-purpose functions
├── validation.bal             # Input validation functions
├── types.bal
├── connections.bal
└── main.bal

Best practices

Practice	Description
Typed parameters	Use specific record types instead of json or anydata.
Error returns	Return error? for operations that can fail.
Isolated functions	Mark functions as isolated. The compiler then verifies there is no unsafe access of shared mutable state, making them safe to call concurrently.
Descriptive names	Start function names with a verb (for example, validateOrder, calculateTotal).

What's next

• Types — Define record types for function parameters and return values.
• Data mapper — Transform data between record types using a visual canvas.
• Connections — Reuse connection configurations across integration artifacts.
• Configurations — Externalize values such as endpoints and credentials.