The C/AL variant data type can contain any variants from OCX and
Automation objects (VT_VARIANT). However, not all these values can
be mapped to C/AL values. For more information, see Using COM Technologies
in C/SIDE.
The variant data type can contain the following C/AL data
types:
-
Record
-
File
-
Action
-
Codeunit
-
Automation
-
Boolean
-
Option
-
Integer
-
Decimal
-
Char
-
Text
-
Code
-
Date
-
Time
-
Binary
-
DateFormula
-
TransactionType
-
InStream
-
OutStream
You can use the variant data type to pass Automation variants
from one external component (Automation or OCX) to another. This
requires that the recipient component can accept the original
variant. You can also assign a C/AL variable to a variant and pass
it to an external component. When you pass C/AL variants ByRef to
an external COM component, small conversion differences may occur.
Therefore, we recommend that you pass C/AL variants ByVal if you do
not need to assign a new value to the C/AL variant in your external
component.
Returning Variants in Internal
Function Calls
The C/AL variant is a complex data type. To return C/AL variants
in function calls, you must pass them in a parameter ByVar (called
ByRef in COM).
Returning DateTime Variants
In the Classic client, if an Automation method returns a
DateTime in a variant, then the time component is removed when the
variant variable is converted to a typed variable. If an Automation
method returns a value in a method argument, then the time
component is not removed. For example, the following code calls an
Automation method that returns a variant and returns a value in one
of the arguments of the method. This example requires that you
create the following variables.
| Variable |
Data type |
|
varAutomation
|
Automation
|
|
varVariant
|
Variant
|
|
returnVariant
|
Variant
|
|
outVariant
|
Variant
|
|
varDate
|
Date
|
|
varTime
|
Time
|
|
varDateReturn
|
Date
|
|
varDateOut
|
Date
|
| |
 Copy Code |
// Create a variant that contains date and time.
varVariant := DATI2VARIANT(varDate, varTime);
// Call an automation method that takes two VT_DATE arguments:
// varVariant and outVariant.
// The method returns a value in the outVariant argument.
returnVariant := varAutomation.MethodDateData(varVariant, outVariant);
varDateReturn := returnVariant;
varDateOut := VARIANT2DATE(outVariant);
|
In this example, you must convert the returnVariant and the
outVariant variables to Date variables in different ways. You can
assign returnVariant, which is the variant that the method returns,
directly to a Date variable because the time component is removed
automatically. You must call VARIANT2DATE on outVariant, which is
the method argument, because the time component is not removed.
In the RoleTailored client, the time component is not removed
from either a variant return value or a variant method argument
when the variant variable is converted to a typed variable.
Variants and Approximation
A C/AL variant contains two allocation areas: one for C/AL
variables and one for Automation and OCX variants. This means that
every time you assign a C/AL variable to a variant, the variant
will contain the same data as the original variable. The conversion
process does not change the data in any way. However, this is not
the case with DATI2VARIANT because it is a VT_VARIANT. When you
assign an external variable to a variant, the variant will also
contain the same data as the original external variable.
Assigning Automation Variants to
FieldRef Values
In Microsoft Dynamics NAV 2009, if an automation method returns
a byte string (bstr) in a variant, you cannot assign that variant
directly to a field that is a Code data type. Instead, you must
first assign the variant to a code variable, and then assign the
code variable to the FieldRef value. For example, the following
code assigns a variant from an automation method to a variable, and
then assigns the variable to a field.
| |
Copy Code |
CodeVariable := AutomationMetodReturningBStrInVariant();
FieldRef.Value := CodeVariable;
|
In previous versions of C/SIDE, you could assign the variant
directly to a Code FieldRef value.
See Also
