Data Provider Subgroup statement

It is one of the components of the Data Provider output-based declarative language. A subgroup is the declarative equivalent of a subroutine in a procedural language. Once declared, could be invoked instead of an element statement  by means of a Subgroup element insertion. 

Syntax 

subgroup <subgroupName>([<parm1>,…,<parmN>])
          <mainGroupList>
endsubgroup

View Syntax conventions

Where:

subgroupName
          It is the name of the subgroup. 

parm₁, …, parm_N 
          It is a list of variables that will be used as a parameter for the subgroup.

mainGroupList
          Is a list of subsequent Group statements.

Samples

Customers
{
   Customer
   {
      Code = CustomerId
      Name = CustomerName
      AddressGroup.Insert(CustomerAddress, CityName)
   }
}

SubGroup AddressGroup(&Street, &City)
Address 
{ 
   Street = &Street
   City = &City 
}
EndSubGroup

A Subgroup can be internal (like this one) or external (defined as another Data Provider). For example, if you have an 'Address' SDT with Street and City as its members, and a Data Provider 'GetAddress' :

Output: Address
Collection: False
Rules: parm( &Street, &City );

Address
{
    Street = &street
    City = &city 
}

You can declare the previous 'GetCustomers' Data Provider like:

Customers
{
    Customer
    {
         Code = CustomerId
         Name = CustomerName
         Address = GetAddress( CustomerAddress, CityName )
    }
}

The Address member of the 'Customer' output SDT must have the 'Address' SDT data type (the output of 'GetAddress'). Otherwise, an error will appear.

Note the difference between 'inserting' a subgroup and 'assigning' an element calling a Data Provider.

One interesting use of this is the recursive one.