Overview

This article is an update to xRM Formula #280, where the rules were executed via a Power Automate Flow. With updated functionality we can now call a Custom Action directly within a Power App, thereby simplifying the implementation and allowing significantly faster synchronous processing times.

Complex rules are often required to be executed as part of a Canvas Power App. North52's business rules engine for Microsoft Dynamics 365 and the Power Platform is a perfect partner when you need to evaluate complex rules in a Canvas App.

In this article, we will use the example of calculating a risk score for Coronary Heart Disease via a Canvas App. The rules and Decision Table structure for the calculation have been outlined in a previous article where the calculation is being made in a Model-Driven App.

This example also shows how stateless processing can be used with North52's business rules engine.

https://www.youtube.com/watch?v=7o083Nd3q9A

Rules for Calculating Coronary Heart Disease Risk

Please see the previous article for the rules table.

North52 Decision Suite Solution

The North52 Decision Suite solution works like this:

• A Custom Action is set up with one input and one output parameter
• The Custom Action is triggered from the Canvas App via the Environment object
  • The Canvas App passes data from the App to the Custom Action
• A Formula is set up on the Custom Action which:
  • Takes the data from the Canvas App
  • Evaluates the data using risk criteria on several Decision Tables
  • Returns results of the Risk Score as JSON
• The JSON is returned to the Canvas App and converted into a Collection
  • The data from the Collection is used to display the Risk Score and Messages on the Canvas App 

Set up Global Action, Formula, Flow and Canvas App

There are 3 parts to configure for this example: Global Action, Formula, and a Canvas App.

Global Action

Set up a Global Action with two parameters:

• PayloadInRiskParametersJSON
  • Type = String
  • Direction = Input
• PayloadOutRiskResultsJSON
  • Type = String
  • Direction = Output

Formula

For details of how to construct the evaluation criteria for the risk score see the xRM Formula #161 - Coronary Heart Disease Risk Score article.

The major differences for this example are:

• The Formula is of Type Action
• Source Entity is N52 Command
• JSON is parsed on the Global Calculations sheet
  • These values are used on the Decision Sheets evaluating the risk
• The Risk Score and Messages are output to the Action parameter PayloadOutRiskResultsJSON

Formula Type

• The Formula is of Type Action bound to the Action Event n52demo_HeartDiseaseRiskAction
• First Decision Sheet calculating the Smoking risk is shown below:

Global Calculations Sheet

• The Global Calculations sheet maps values from the PayloadInRiskParametersJSON input parameter to individual calculations that can be easily referenced in the Decision Sheets (like the Smoking one above)
• Firstly the PayloadInRiskParametersJSON input parameter is assigned to the North52 internal variable called responsecontent
• Then individual values are assigned, for example, Current Smoker is assigned on row 4 

Risk Calculation Sheet

• Column J is an incremental inline calculation
• Column K is an inline calculation that calls a parameterized Global Action (see next image below for details)
  • The highlighted cell K4 shows the BuildJSON Global Action with the first parameter 'Smoke Risk' and the second parameter 'The patient has a smoke risk.'  

BuildJSON Global Action

• The BuildJSON Global Action shows how we are constructing JSON to collate the messages for each matching risk

• An example of the output for this Global Action:

  {
    "risktype": "Smoke Risk",
    "message": "The patient has a smoke risk."
  }

Action Response Sheet

• This sheet provides the response to the Action's PayloadOutRiskResultsJSON output parameter
• The highlighted contents of cell A4 shows construction of the JSON, including the Risk Messages JSON from above

• An example of the output for this output parameter:

  {
    "Results": {
      "RiskScore": 3,
      "RiskMessages": [
        {
          "risktype": "Smoke Risk",
          "message": "The patient has a smoke risk."
        },
        {
          "risktype": "Dyslipidemia Risk",
          "message": "The patient has a dyslipidemia risk."
        },
        {
          "risktype": "Family History Risk",
          "message": "The patient has a family history risk."
        }
      ]
    }
  }

Canvas App

Within the Canvas App there are two important parts to review:

• The OnSelect property of a button to collect the values and submit them to the Custom Action
• The DataTable which shows the messages that have been returned as part of the JSON response

OnSelect of Button

• The values from many input objects are collated in a Collection called FormulaData (1)

• This FormulaData collection is passed to the Environment.n52demo_HeartDiseaseRiskAction({PayloadInRiskParametersJSON:JSON(FormulaData)}).PayloadOutRiskResultsJSON (2)
• The Custom Action returns the results from the North52 calculation and adds this to a variable called PayloadOutRiskResultsJSON (2)
• The variable Score is set by parsing the JSON Set(Score, Value(ParseJSON(PayloadOutRiskResultsJSON).Results.RiskScore)); (3)
• The Risk Messages are added to a collection called RiskMessages by parsing the JSON (4)

DataTable

• A DataTable is shown using the RiskMessages Collection