Create an Entity

Procedure

Let's create a compound entity because if you master that, you'll also know how to create elementary entities. You'll create the compound Invoice entity as shown above, including the calculation of Amount at the InvoiceItem level and the TotalAmount at the Invoice level.

For compound entities, it's necessary to work bottom-up because parent entities require child entities to be available. So, first, create ProductItem, then InvoiceItem, and finally, Invoice:

Step 1: Create the ProductItem entity

1. Create a ruleset named TotalInvoiceAmount.

2. Create an entity named entProductItem.

3. Click Add property.
   ↳ The Input/Property page opens.

4. In The Name field, enter ProductID. And in the Type list, select string.

5. Save the property.

6. Repeat steps 3 to 5 to create the Description property as a string and the Price property as a number.
   ↳ Finally, your entity should look like this:

   

Step 2: Create the InvoiceItem entity

1. Create an entity named entInvoiceItem.

2. Add a property named Count (Type=number).

3. Add a property named Product. And in the Type list, select entProductItem.
   ↳ Now, entInvoiceItem and entProductItem are connected, and entInvoiceItem has become a compound entity. Rulecube shows this with a little cube icon in front of the entInvoiceItem entity:

   

4. Add a calculated property for Amount (Type=number) and set its Expression to:

   Count * Product.Price

   Explanation
   Because entInvoiceItem and entProductItem are connected, you can use the Product.Price to calculate the amount for invoice items.

5. Save the entity.
   ↳ The content of entInvoiceItem should look like this:

   

   Notice that Rulecube places the of input in front of regular properties and the of rule in front of calculated properties.

Step 3: Create the Invoice entity

1. Create an entity named entInvoice.

2. Add a property named InvoiceItems and set its Type to array with Sub type = entInvoiceItem.
   ↳ By defining this property as an array, an invoice can have multiple items. Furthermore, entInvoice and entInvoiceItem are connected now. And because entInvoiceItem is connected to entProductItem, entInvoice is also connected to entProductItem.

3. Add a calculated property for TotalAmount (Type=number) and set its Expression to:

   InvoiceItems.sum(item => item.Amount)

   Explanation
   This is an arrow function that summarizes all the item amounts into the TotalAmount.

4. Save the entity.
   ↳ Your compound entity structure now should look like this:

   

Step 4: Test your ruleset

Try out the ruleset and enter input like this:

{
  "Invoice": {
    "InvoiceItems": [
      {
        "Product": {
          "ProductID": "PK-207-U",
          "Description": "Rubber bands",
          "Price": 11.75
        },
        "Count": 8
      },
      {
        "Product": {
          "ProductID": "KD-883-J",
          "Description": "6mm tube - 1mtr",
          "Price": 5.15
        },
        "Count": 5
      }      
    ]
  }
}

After executing, you should get a result like this:

{
  "InvoiceItems": [
    {
      "Product": {
        "ProductID": "PK-207-U",
        "Description": "Rubber bands",
        "Price": 11.75
      },
      "Count": 8,
      "Amount": 94
    },
    {
      "Product": {
        "ProductID": "KD-883-J",
        "Description": "6mm tube - 1mtr",
        "Price": 5.15
      },
      "Count": 5,
      "Amount": 25.75
    }
  ],
  "TotalAmount": 119.75
}

With the amount calculated per item and the total amount calculated for the invoice.

Additional resources

If you have a JSON schema or an XSD for your entity structure, Rulecube has a much easier and quicker way to create entities as described in the Drag and Drop guide.