Custom Properties

Adding Custom Properties to a Model

Harmony Core allows developers to extend code generated data models by adding custom properties. One common use case for this capability is to add "calculated" properties, or other properties that might be useful to a consumer of the data.

• If the affected data model class has not already been customized via the addition of a custom partial class, then do so.

  For example, to customize a data model named Customer we recommend you add a source file named Customer.Custom.dbl that initially containins:

  namespace Services.Models
  
      public partial class Customer
  
  
      endclass
  
  endnamespace
  

• Add a property to the custom data object partial class to represent the custom property.

  • Add a getter method to the property and add code that returns the custom property value.
  • Add a setter method to the property. If it is valid for the value of the custom property to be updated then have the setter method update the value, otherwise have the setter method throw an exception.

  For example, you might add a property like this:

  namespace Services.Models
  
      public partial class Customer
  
          public property AvailableCredit, decimal
              method get
              proc
                  mreturn this.CreditLimit - this.AccountBalance
              endmethod
              method set
              proc
                  throw new ApplicationException("Property AvailableCredit may not be updated.")
              endmethod
          endproperty
  
      endclass
  
  endnamespace
  

• If the affected data model metadata class has not already been customized via the addition of a custom partial class, then do so.

  For example, to customize a metadata class named CustomerMetaData we recommend you add a source file named CustomerMetaData.Custom.dbl that initially containins:

  namespace Services.Models
  
      public partial class CustomerMetaData
  
  
      endclass
  
  endnamespace
  

• If the custom metadata class does not already contain a method named InitializeCustomFields then add one, like this:

  namespace Services.Models
  
      public partial class CustomerMetaData
  
          private method InitializeCustomFields, void
          proc
  
          endmethod
  
      endclass
  
  endnamespace
  

• Add code to the InitializeCustomFields method to add the definition of the custom field to the metadata class. For example:

  namespace Services.Models
  
      public partial class CustomerMetaData
  
          private method InitializeCustomFields, void
          proc
             AddFieldInfo("AvailableCredit","DECIMAL",8,0,2,false)
          endmethod
  
      endclass
  
  endnamespace
  

The parameters to the AddFieldInfo call are as follows:

• Property name
• Data type name. Supported values are ALPHA, BINARY, DATE, DECIMAL, IMPLIED, INTEGER, JULIAN, TIME, USER ALPHA, USER DATE, USER NUMERIC, TAG_LITERAL, DATAOBJECT, COLLECTION and COMPOSITE.
• Field size (bytes)
• Position in record
• Number of decimal places (or zero)