Value Types vs. Reference Types
ECR references value types and reference types .
Value types include simple types (e.g., char, int, and float), enum types, and structure types. Reference types include class types, interface types, delegate types, and array types. Value types differ from reference types in that variables of the value types directly contain their data, whereas variables of the reference types store references to objects.
With reference types, it is possible for two variables to reference the same object, and thus possible for operations on one variable to affect the object referenced by the other variable. With value types, the variables each have their own copy of the data, and it is not possible for operations on one to affect the other.
In ECR, pretty much all types (*<something>) are value types, except: *object, *string, *form, and as of 7.1 enumerations (BegEnum).
- Fields declared with a value
type have a default value which depends on the particular type (like 0 for
numerics or blanks for
*char). - Fields declared with a reference type all have the same
default value which is
*Nothing.
** Therefore they must be initialized before they can be used .** You can test for*nothingin conditional expressions (eg.IF (mystring = *nothing) …)
Related Sections
Value Types and Reference Types
Explains the difference between value and reference types in terms of declaration syntax, usage, and semantics.
DataTypes as Classes and Structures
Describes how Encore RPG datatypes are implemented in the underlying .NET Framework.