Mega Code Archive
Vartypemask - mask for the meta-type part of a variant variable
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const VarTypeMask = $0FFF;
Description
The VarTypeMask constant provides a mask for use with the VarType function. It allows the meta-type part of a Variant to be excluded when checking for the basic data type of a Variant.
The data type is a 16 bit value, split into a high order 4 bits and a low order 12 bits. The high order bits give a meta data type:
varArray : If the Variant holds an array of data
varByRef : If the Variant indirectly refers to data
The low order bits contain one of the following values:
varEmpty
varNull
varSmallint
varInteger
varSingle
varDouble
varCurrency
varDate
varOleStr
varDispatch
varError
varBoolean
varVariant
varUnknown
varShortInt
varByte
varWord
varLongWord
varInt64
varStrArg
varString
varAny
Related commands
Variant A variable type that can hold changing data types
VarType Gives the current type of a Variant variable
Example code : Illustrating a few Variant types using VarTypeMask
var
myVar : Variant;
begin
// Assign various values to a Variant
// and then show the resulting Variant type
ShowMessage('Variant value = not yet set');
ShowBasicVariantType(myVar);
// Simple value
myVar := 123;
ShowMessage('Variant value = 123');
ShowBasicVariantType(myVar);
// Calculated value using a Variant and a constant
myVar := myVar + 456;
ShowMessage('Variant value = 123 + 456');
ShowBasicVariantType(myVar);
myVar := 'String '+IntToStr(myVar);
ShowMessage('Variant value = String 579');
ShowBasicVariantType(myVar);
end;
// Show the type of a variant
procedure TForm1.ShowBasicVariantType(varVar: Variant);
var
typeString : string;
basicType : Integer;
begin
// Get the Variant basic type :
// this means excluding array or indirection modifiers
basicType := VarType(varVar) and VarTypeMask;
// Set a string to match the type
case basicType of
varEmpty : typeString := 'varEmpty';
varNull : typeString := 'varNull';
varSmallInt : typeString := 'varSmallInt';
varInteger : typeString := 'varInteger';
varSingle : typeString := 'varSingle';
varDouble : typeString := 'varDouble';
varCurrency : typeString := 'varCurrency';
varDate : typeString := 'varDate';
varOleStr : typeString := 'varOleStr';
varDispatch : typeString := 'varDispatch';
varError : typeString := 'varError';
varBoolean : typeString := 'varBoolean';
varVariant : typeString := 'varVariant';
varUnknown : typeString := 'varUnknown';
varByte : typeString := 'varByte';
varWord : typeString := 'varWord';
varLongWord : typeString := 'varLongWord';
varInt64 : typeString := 'varInt64';
varStrArg : typeString := 'varStrArg';
varString : typeString := 'varString';
varAny : typeString := 'varAny';
varTypeMask : typeString := 'varTypeMask';
end;
// Show the Variant type
ShowMessage('Variant type is '+typeString);
end;
Show full unit code
Variant value = not yet set
Variant type = varEmpty
Variant value = 123
Variant type = varByte
Variant value = 123 + 456
Variant type = varInt64
Variant value = String 579
Variant type = varString
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