7 - Writing a custom aggregation Function

📖 Task Introduction

You want to provide your Workshop module users with a metric card highlighting the percentage of unresolved alerts in the queue. Workshop can natively calculate and present numeric aggregations, but sometimes you may need to calculate a metric using business logic that is not available via the Workshop front-end.

We can extend Workshop’s capability with a Function that supplies the figure we need. In this task, you’ll add a custom Function as a method in the MyFunctions class.

🔨 Task Instructions

1. Open the ../src/index.ts file in your repository.

2. We need to create space for a new function inside the MyFunctions class. Place your cursor after the closed brace on line 8 and hit enter twice.

3. Insert the following code block, being careful to ensure the @Function() decorator and public... lines are aligned with the function above.

   • Also replace jmeierPercentUnresolved with a dedicated name you'll recognize (for example, replace jmeier with your name) and replace JmeierFlightAlert with your API name.
   • The comments in the code describe the operations being performed.

   @Function()
       //Take in an array of flight alert objects aliased as "alerts" 
       //and return a Double
       public jmeierPercentUnresolved(alerts: JmeierFlightAlert[]): Double {
       
       //Check that your array actually has objects in it, otherwise return a "0"
           if (alerts.length === 0) {
               return 0;
           }
       
       //Cycle through your array incrementing a variable ("numberUnresolved") 
       //by 1 every time it encounters an alert without a resolved status
           let numberUnresolved = 0;
           for (const alert of alerts) {
               if (alert.status != "Resolved") {
                   numberUnresolved++;
               }
           }
       
       //return the number of un-resolved alerts divided by the 
       //length of the original array
           return numberUnresolved/alerts.length;
       }
   

4. If your Code Assist is running, you’ll see that the output type of Double is underlined in red, indicating an issue with the code. In short, your repository has discovered a type that has not been imported.

   • Add Double to the Functions API import statement: import { Function, Integer, Double } from "@foundry/functions-api";