Variant Data Type

项目
10/18/2021

The C/AL variant data type can contain many C/AL data types or any variants from OCX and Automation objects. However, not all these values can be mapped to C/AL values. For more information, see Using COM Technologies in Microsoft Dynamics NAV.

The variant data type can contain the following C/AL data types:

Action
Automation
BigInteger
BigText
Boolean
Byte
Char
Code
Codeunit
Date
DateFormula
DateTime
Decimal
Duration
GUID
InStream
Integer
Option
OutStream
Record
RecordRef
Text
Time
TransactionType

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 have 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).

Passing DateTime variables to Automation

It is not possible to pass a C/AL DateTime variable to Automation. However, you can convert the C/AL DateTime to a variant, and then pass it to Automation. The following examples shows how to pass a DateTime to Automation. This example requires that you create the following variables.

Variable	Data type
varAutomation	Automation
varVariant	Variant
varDateTime	DateTime

varDateTime := CURRENTDATETIME;
varVariant := varDateTime;
varAutomation.MethodDateData(varVariant);

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 every time that 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 2013, if an Automation method returns a byte string (bstr) in a variant, you cannot assign that variant 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.

CodeVariable := AutomationMetodReturningBStrInVariant();
FieldRef.Value := CodeVariable;

In earlier versions of Microsoft Dynamics NAV, you could assign the variant to a Code FieldRef value.

通过

Variant Data Type

Returning Variants in Internal Function Calls

Passing DateTime variables to Automation

Variants and Approximation

Assigning Automation Variants to FieldRef Values

See Also

Reference

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