Using Caché Objects - InterSystems Documentation

Object-Specific ObjectScript Features
For example, suppose there is an application with an Accounting.Order class and an
Accounting.Utils class. The Accounting.Order.CalcTax method calls the
Accounting.Utils.GetTaxRate and Accounting.Utils.GetTaxableSubtotal methods, passing the
current instance's city and state values to GetTaxRate and passing the list of items ordered
and relevant tax-related information to GetTaxableSubtotal. CalcTax then uses the values
returned to calculate the sales tax for the order. Hence, its code is something like:
Method CalcTax() As %Numeric
{
Set TaxRate = ##Class(Accounting.Utils).GetTaxRate(##this)
Write "The tax rate for ",..City,", ",..State," is ",TaxRate*100,"%",!
Set TaxableSubtotal = ##class(Accounting.Utils).GetTaxableSubTotal(##this)
Write "The taxable subtotal for this order is $",TaxableSubtotal,!
Set Tax = TaxableSubtotal * TaxRate
Write "The tax for this order is $",Tax,!
}
The first line of the method uses the ##Class syntax (described above) to invoke the other
class' method; it passes the current object to that method using the ##this syntax. The second
line of the method uses the .. syntax (also described above) to get the values of the instance's
City and State properties. The action on the third line is similar to that on the first line.
The Accounting.Utils class' GetTaxRate method can then use the handle to the passed-in
instance to get handles to various properties — for both getting and setting their values:
ClassMethod GetTaxRate(OrderBeingProcessed As Accounting.CustOrder) As %Numeric
{
Set LocalCity = OrderBeingProcessed.City
Set LocalState = OrderBeingProcessed.State
// code to determine tax rate based on location and set
// the value of OrderBeingProcessed.TaxRate accordingly
Quit OrderBeingProcessed.TaxRate
}
The GetTaxableSubtotal method also uses the handle to the instance to look at its properties
and set the value of its TaxableSubtotal property.
Hence, the output at the Caché terminal from invoking the CalcTax method for MyOrder
instance of the Accounting.Order class would be something like:
>Do MyOrder.CalcTax()
The tax rate for Cambridge, MA is 5%
The taxable subtotal for this order is $79.82
The tax for this order is $3.99
182 Using Caché Objects