Scalar-function rule

Introduction

Rules in Casewhere are not limited to boolean predicates. A scalar-function rule performs logic and returns a value of any type. Extracting computing logic into reusable rules is a best practice — it keeps workflows clean and makes the logic available across different parts of your solution.

Rule syntax

Keywords

The following keywords are available in scalar-function rules:

Name	Type	Description
@user	DslUser	The user in context. See access rule for the full DslUser reference.
@parameters	DynamicDataObject	The parameters passed to the rule. Access attributes using the dot operator (e.g., @parameters.address).
@apiFactory	IManagedApiFactory	To construct Casewhere API objects. Read here for the full list of available APIs.

Examples

Example 1: Unit conversion

A rule named "Convert Meter To Centimeter" that converts a meter value to centimeters:

@parameters.meterValue * 100

Evaluate the rule in a workflow scripted activity using IRuleApi:

var ruleApi = ctx.Use<IRuleApi>();
 
var parameters = new Dictionary<string, object>();
parameters["meterValue"] = 1;
 
var cm = ruleApi.Eval<int>("Convert Meter To Centimeter", parameters);

Example 2: Reusable data query

A rule named "Find Products By SKU" that queries products by their SKU code:

#predicate 
 
var dataApi = @apiFactory.Get<IDataApi>();
var filter = FilterBuilder.Create().Eq("SKU", @parameters.SKU).Build();
var result = dataApi.Search(DataObjectApiQuery
    .For("Product")
    .FilterBy(filter));
 
return result.Data;

Evaluate the rule in a workflow scripted activity using IRuleApi:

var ruleApi = ctx.Use<IRuleApi>();

var parameters = new Dictionary<string, object>();
parameters["SKU"] = "LAPTOP";
 
var products = ruleApi.Eval<List<DynamicDataObject>>("Find Products By SKU", parameters);