Data sources
Custom List functions (Lua)
In addition to defining columns and retrieving data, a CustomListBase can define callable functions that are executed directly from Peakboard Designer Lua scripts. These functions enable computations, transformations or actions (for example sending data to an API or performing calculations) triggered live inside a Peakboard visualization.
Defining a function
Functions are declared within the GetDefinitionOverride method of the CustomListBase class. Each function is a CustomListFunctionDefinition added to the Functions collection of the returned CustomListDefinition. A function definition describes its name (as called from Lua), its input parameters and its return parameters:
using Peakboard.ExtensionKit;
namespace CalcDemo;
[Serializable]
class CalcDemoCustomList : CustomListBase
{
protected override CustomListDefinition GetDefinitionOverride()
{
return new CustomListDefinition
{
ID = "CalcDemoList",
Name = "Calculation demo",
PropertyInputPossible = false,
Functions =
{
new CustomListFunctionDefinition()
{
Name = "calc",
Description = "Performs basic arithmetic operations on two numbers.",
InputParameters = new CustomListFunctionInputParameterDefinitionCollection
{
new CustomListFunctionInputParameterDefinition
{
Name = "a",
Description = "The first numeric operand.",
Optional = false,
Type = CustomListFunctionParameterTypes.Number
},
new CustomListFunctionInputParameterDefinition
{
Name = "b",
Description = "The second numeric operand.",
Optional = false,
Type = CustomListFunctionParameterTypes.Number
},
new CustomListFunctionInputParameterDefinition
{
Name = "op",
Description = "Arithmetic operator (+, -, *, /).",
Optional = false,
Type = CustomListFunctionParameterTypes.String
}
},
ReturnParameters = new CustomListFunctionReturnParameterDefinitionCollection
{
new CustomListFunctionReturnParameterDefinition
{
Name = "result",
Description = "The result of the arithmetic operation.",
Type = CustomListFunctionParameterTypes.Number
}
}
}
}
};
}
}
| Property | Type | Description |
|---|---|---|
Name |
string |
The Lua-accessible name of the function. |
Description |
string |
Tooltip / description shown in the Designer. |
InputParameters |
CustomListFunctionInputParameterDefinitionCollection |
The parameters accepted by the function. |
ReturnParameters |
CustomListFunctionReturnParameterDefinitionCollection |
One or more values the function returns. |
Type |
CustomListFunctionParameterTypes |
Supported types: Number, String, Boolean. |
Optional |
bool |
Whether an input parameter is optional. |
Executing a function
When a Lua script inside Peakboard calls a function (e.g. Data.CalcDemoList:calc(10, 5, "+")), the framework invokes ExecuteFunctionOverride in your CustomListBase class. Read the input parameters from the context.Values collection (in the same order they were defined) and return results via a CustomListExecuteReturnContext:
protected override CustomListExecuteReturnContext ExecuteFunctionOverride(CustomListData data, CustomListExecuteParameterContext context)
{
// Access parameters in the same order they were defined in GetDefinitionOverride()
double varA = double.Parse(context.Values[0].StringValue); // first parameter: "a"
double varB = double.Parse(context.Values[1].StringValue); // second parameter: "b"
string op = context.Values[2].StringValue; // third parameter: "op"
var result = new CustomListExecuteReturnContext();
switch (op)
{
case "+": result.Add(varA + varB); break;
case "-": result.Add(varA - varB); break;
case "*": result.Add(varA * varB); break;
case "/": result.Add(varA / varB); break;
}
return result;
}
Like the other overrides, ExecuteFunctionOverride must be protected, must not be async, and should be wrapped completely in try/catch (see the implementation rules).
