Embarcadero Delphi Strings Assignment


Example

Assigning string to different string types and how the runtime environment behaves regarding them. Memory allocation, reference counting, indexed access to chars and compiler errors described briefly where applicable.

var
  SS5: string[5]; {a shortstring of 5 chars + 1 length byte, no trailing `0`}
  WS: Widestring; {managed pointer, with a bit of compiler support}
  AS: ansistring; {ansistring with the default codepage of the system}
  US: unicodestring; {default string type}
  U8: UTF8string;//same as AnsiString(65001)
  A1251: ansistring(1251); {ansistring with codepage 1251: Cryllic set}
  RB: RawbyteString; {ansistring with codepage 0: no conversion set}
begin
  SS5:= 'test'; {S[0] = Length(SS254) = 4, S[1] = 't'...S[5] = undefined}
  SS5:= 'test1'; {S[0] = 5, S[5] = '1', S[6] is out of bounds}
  SS5:= 'test12'; {compile time error}
  WS:= 'test'; {WS now points to a constant unicodestring hard compiled into the data segment}
  US:= 'test'+IntToStr(1); {New unicode string is created with reference count = 1}
  WS:= US; {SysAllocateStr with datacopied to dest, US refcount = 1 !}
  AS:= US; {the UTF16 in US is converted to "extended" ascii taking into account the codepage in AS possibly losing data in the process}  
  U8:= US; {safe copy of US to U8, all data is converted from UTF16 into UTF8}
  RB:= US; {RB = 'test1'#0 i.e. conversion into RawByteString uses system default codepage}
  A1251:= RB; {no conversion takes place, only reference copied. Ref count incremented }