Calculation

Reference documentation for a Calculation object

Overview

A Calculation object provides a dynamic, calculated value in a Table in a Database Server. A calculation is a JavaScript function, which is always computed on-demand, whenever it is displayed or referenced in code. It can be added to the UI the same as any other Data Provider. A calculation is read-only.

File Structure

The code for a Calculation is stored in a script file in a Solution directory -> "datasources" directory -> "table-name" directory. The file has the same name as the table "_calculation", with a .js extension. For example, the products table would have the calculation file products_calculation.js. Nesting file path: "solution/datasources/server-name/table-name/table-name_calculations.js"

Properties Summary

The following properties can be set for a Calculation object.

Property	Summary
Name	The name of the calculation. It is also the same name as the function that returns the value.
Returned Type	The data type of the object that will be returned from the calculation
Code	This is the JavaScipt function that defines the calculation.
Stored	A calculation is said to be stored when a physical column with the same name exists on the table

Properties Details

Name

The name of the calculation. It is also the same name as the function that returns the value.

Returned Type

The data type of the object that will be returned from the calculation. All data types are generalized to one of five standard types:

• DATETIME

• INTEGER

• MEDIA

• NUMBER

• TEXT

Code

This is the JavaScript function that defines the calculation. It takes no arguments and should return a value. Other data providers from this table, related data sources, and scope variables can be used.

Example

/**
 * Gets the subtotal of the order line
 * @properties={type:8,typeid:36,uuid:"214515EE-2D6C-4C0B-AF3D-5C4C0E165952"}
 */
function subtotal()
{
	return quantity * unitprice;
}

Stored

A calculation is said to be stored when a physical column with the same name exists on the table. The real column can be updated opportunistically when a calculation runs.

Stored calculations can be unpredictable, there is no guaranteed way to know exactly when they will run to update the underlying column in the table, especially if they are complex or depend on other calculations or methods.

A better approach is to use to catch changes to the table and make updates to other columns if necessary.