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Pointers (Delphi and Delphi Prism Cross Reference Guide)

By Mike Prestwood

Delphi versus Delphi Prism: A side by side comparison between Delphi and Delphi Prism.

Data Structures

Data structures allow you to store and work with data. Common data structures include arrays, associative arrays, etc.


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General Info: Pointers / References

A pointer is a variable type that allows you to refer indirectly to another object. Instead of holding data, a pointer holds the address to data -- the address of another variable or object. You can change the address value a pointer points to thus changing the variable or object the pointer is pointing to.

A reference is a type of pointer that cannot change and it must always point to a valid storage (no nulls).


Although pointer data types in Delphi coding are less important and not required for most general coding, Delphi fully supports developer defined pointers. Use a carrot (^) to declare a pointer data type. Use the @ operator or Addr function to return the current address of a variable.

Delphi provides typed pointer types such as PChar and PExtended as well as a generic point to anything Pointer type.

Nil is a special pointer value that you can assign to any type of pointer. Nil never points to any valid memory and indicates an unassigned or empty pointer.

Syntax Example:
//Declare a pointer of type integer.
PCounter : ^Integer;
//Assign a value to the location of a pointer.
//Also known as dereferencing.
PCounter^ := 8;
//Assign address of A to B.
PointerB := @PointerA;  //or...PointerB := Addr(PointerA);
Delphi Prism: 

Although pointer data types in Prism coding are less important than in other languages such as C++, Prism does support developer defined pointers. Use the ^ operator to declare a pointer data type. Use the @ operator to return the current address of a variable.

In .Net managed coding the use of pointers is not safe because the garbage collector may move memory around. To safely use pointers, use the unsafe keyword. However, avoid unsafe code if possible.

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