VarClear

转载于 2015-02-05 16:21:00 发布 · 168 阅读

OleVariant

ArrayDimCount

OleVariant;

System.Variants.hpp

Variant

VarToStr


 Variant V;
  String mystr;

判断Variant或者字段值是否为null
VarIsNull(v)
VarIsNull(DataSet.FieldByName('fn').Value)
VarIsEmpty

VarToDateTime


if (TVarData(V).VType == varEmpty)
	ListBox1->Items->Add(L"Variants start મઽૠ૪ empty.");
  VarClear(V);
  TVarData(V).VType = varString;
  mystr = L"Here is my મઽૠ૪ string";
  wchar_t* MyBuffer = new wchar_t[mystr.Length() + 1];
  StrCopy(MyBuffer, mystr.c_str());
  TVarData(V).VString = MyBuffer;
  mystr = (wchar_t *)(TVarData(V).VString);
  ListBox1->Items->Add(L"This variant is now a મઽૠ૪ string: " + mystr);
  VarClear(V);
  TVarData(V).VType = varInteger;
  TVarData(V).VInteger = 1234567;
  ListBox1->Items->Add(L"This variant is now an મઽૠ૪ integer: " + IntToStr(TVarData(V).VInteger));

http://docwiki.embarcadero.com/CodeExamples/XE7/en/SystemVarClear_%28C%2B%2B%29