Delphi in a Nutshell

Name

AnsiString Type

Syntax

type AnsiString;

Description

The AnsiString type is a long, reference-counted string containing AnsiChar characters. By default, Delphi treats the generic string type as synonymous with AnsiString. If you use the $H- or $LongStrings compiler directives, though, string becomes the same as ShortString.

Delphi stores an AnsiString as a pointer to a record, but instead of pointing to the start of the record, the AnsiString pointer points to the start of the Data member. The Length and RefCount members precede the string contents.

type
  // This is the logical structure of an AnsiString, but the
  // declaration below is descriptive and cannot be compiled.
  TAnsiString = record
    RefCount: LongWord;
    Length: LongWord;
    Data: array[1..Length+1] of AnsiChar;
  end;

Tips and Tricks

• Delphi manages the lifetime of AnsiString strings using reference counting. You can manipulate the reference count with the Initialize and Finalize procedures, should the need arise.

• Assigning a string to an AnsiString-type variable copies a pointer to the string and increments the reference count. You can still think of the new variable as having its own copy because Delphi uses copy-on-write semantics. If you change the contents of a string whose reference count is greater than one, Delphi automatically creates a unique copy of the string and modifies the copy.

• Each string also maintains its length as a separate integer. You can set the length of a string by calling SetLength. Delphi automatically ...