Variant
From Xojo Documentation
A Variant is a special data type that can contain any type of data, including arrays. Use the VarType function or the Variant's Type method to determine the data type of a Variant.
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Class Constants
The following class constants can be used to determine the data type of the Variant using the Type method. If the variant is an array, use the ArrayElementType function to test for the type of array and compare the result to the class constants for scalars.
| Class Constant | Integer Value | Description |
|---|---|---|
| TypeArray
Introduced 2008r1
|
4096 | Array |
| TypeBoolean | 11 | Boolean |
| TypeCFStringRef | 21 | CFStringRef |
| TypeColor | 16 | Color |
| TypeCString | 18 | CString |
| TypeCurrency | 6 | Currency |
| TypeDate | 7 | Date |
| TypeDateTime | 38 | DateTime |
| TypeDouble | 5 | Double |
| TypeInt32 | 2 | Int32 32 bit integer. |
| TypeInt64 | 3 | Int64 or UInt64. 64 bit integer. |
| TypeNil | 0 | Nil |
| TypeObject | 9 | Object |
| TypeOSType | 23 | OSType |
| TypePString | 20 | PString |
| TypePtr | 26 | Ptr |
| TypeSingle | 4 | Single |
| TypeString | 8 | String |
| TypeStructure
Introduced 2008r1
|
36 | Structure |
| TypeText | 37 | Text |
| TypeWString | 19 | WString |
If a Variant stores an array, the Type method will equal Variant.TypeArray logically OR'ed with the array element type. You can get the element type by calling ArrayElementType.
Notes
Particularities of the Variant object
The default value of a Variant is Nil. However, unlike other objects, you can use the above methods with a Nil Variant without raising a NilObjectException.
For example, the following is valid for a Variant but not for any other Object:
Var vType As Integer // To store the variant type
vType = v.Type // It does not raise NilObjectException
This peculiarity allows you to use the method IsNull instead of v = Nil. They both give the same result:
Variants do not have a specific default value, but will instead get the default value of whatever type they are converted to (see the next section).
Automatic conversion of values
When you assign a variant to a string, numeric, or date variable, value of the variant is converted to the variable's data type. For example,
If there is any ambiguity concerning the type conversion of a variant, you should use one of the properties of the Variant class to force the compiler to convert the variant to the desired type. In this example, the Product number is supposed to be the string concatenation of the Model number and the Part Number. To do this, use the StringValue property to specifically tell the compiler to do what you want:
model = 100
partNumber = 546
product = model + partNumber // product=646
product = model.StringValue + partNumber.StringValue // product="100546"
Or, you could just type the variables as String and do string concatenation directly.
Variants used in an expression convert themselves to the type of the other operand, no matter what kind of data they contain, instead of deferring the type-conversion until runtime. This only affects expressions involving a variant operand and an operand of some other type, not expressions in which both operands are variants.
Consider the following example:
The comparison:
returns False since v is being treated as an Integer and will round down to 0.
If you instead use:
the comparison returns True.
The comparison:
also returns True.
Conversion from Nil
If you assign a Nil variant to an intrinsic type, then the value will be the default value for the intrinsic type:
Var b As Boolean = v // False
Var d As Double = v // 0.0
Var i As Integer = v // 0
Var s As String = v // ""
See Also
IsNumeric, VarType functions; Dictionary classes;