What is Self / Current_Object << Back

The keyword "Self" (or if you are an old timer like myself, you might refer that as "Current_Object") is the starting point for resolving the object reference. It contains the object handle your code is currently at. The value stored insides "Self" changes depends on which object you are in. Let's look at the following example

Use UI

Procedure ShowSelf
	Showln (Name(Self)) " " Self
End_Procedure

Object oObject1 is a cObject
	Send ShowSelf
End_Object

Object oObject2 is a cObject
	Send ShowSelf
End_Object

InKey FieldIndex

Notice that depending who calls the "ShowSelf" procedure, it will display different object name on line 4. Let's see what else we can do with "Self"

Use UI

Procedure ShowSelf
	Showln (Name(Self)) " " Self
End_Procedure

Object oObject1 is a cObject
	Send ShowSelf
End_Object

Object oObject2 is a cObject
	Move Self to FieldIndex        // Save the value of "Self" to a temp variable
	Move (oObject1(Self)) to Self  // Pretend that you are in oObject1
	Send ShowSelf
	Move FieldIndex to Self        // Restore the value of "Self"
End_Object

InKey FieldIndex

You will see that program is going to output "oObject1" twice because we changed the value in "Self" before sending "ShowSelf". You can think of "Self" is just a global variable that is changed by the VDF runtime auto-magically, depending on where your code is at. However, since it's a variable, that means its value can be changed by you. It is unusual to change the content in "Self", but it will come in extremely handy if you are doing "Eval" on the fly. We will deep dive into "Eval" in the future article.