Difference between Ansistring, Widestring, Unicodestring, Shortstring and String and how to convert

Question

During my Delphi learning I see implementations that use AnsiString,WideString, UnicodeString,ShortString and String but I don’t know the difference between them.

Another thing that always occurs to me is that I try to save some kind in another and it returns me the error that must be converted, however I always have difficulty to do it the right way.

Answer 1

• AnsiString: string composed of ASCII characters. Each Char has exactly 1 bytes. A pointer to a AnsiString (^AnsiString) amounts to char* in C;

• WideString: exists only for compatibility with Windows. Each Char has 2 bytes, and must be used in Win32 functions with parameters LPWSTR, performing a cast for PWChar;

• UnicodeString: Unicode string. By default UTF-16 (or at least it was when I last searched), but can assume other encodings such as UTF-8.

• ShortString: equals old Pascal string, with its limitation of 255 characters.

• String: in the newer versions of Delphi (2007 onwards), UnicodeString. In the old days it amounted to AnsiString.

So much AnsiString how much UnicodeString are more than a simple array of Char, they have code page information and size. However, to facilitate the cast of these types to PChar and its variations, this information is in the addresses previous to the returned by the operator @.

Conversion

The conversion between them is done automatically. Only care that should be taken, is that data may be lost during conversion due to type not supporting any feature of source string.

For example, convert UnicodeString for AnsiString, there may be loss due to Unicode characters occupying more than 1 byte.

Conversion of AnsiString (or UnicodeString) for ShortString, there will be data loss if the source string is greater than 255 (Length(origem) > 255).