Variant (Variable type)

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Variant type and NULL values
Type of a variant
Class property on variants
Named subelements
Indexed subelements
Nesting named and indexed subelements

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Variant (Variable type)

In french: Variant

The Variant type is used to:

store any simple value: boolean, numeric (Currency, Real, Integer, etc.), characters and character string, date (Date, Time, DateTime and Duration), etc.
store named or indexed subelements.
store any complex value: structures, classes, advanced types, arrays, associative arrays, queues, stacks and lists.
handle the NULL value in WLanguage.
store interactions with ActiveX objects and Automation programming.

Example

nValue is Variant = 10
nValue = EDT_Edit1
nValue = Customer.Name

Syntax

Declaring and assigning a Variant type Hide the details

<Variable name> is Variant = <Value>

OR

<Variable name> is Variant
<Variable name> = <Value>

<Variable name>:

Name of the variable to declare.

<Value>:

Value to be assigned to the variable. One of the following values can be assigned to a Variant variable:
any literal value,
the content of a variable,
the content of a simple control,
the content of an item.

Remarks

Variant type and NULL values

To specify that a Variant variable contains no value, use the NULL constant.

Remarks:

for a Variant type, NULL means "Not assigned".
for a Numeric type, NULL means "equal to 0".

nVal is int
IF vVal = Null THEN ... // the test returns True because nVal=0
nVal = 5
IF vVal = Null THEN ... // the test returns False because nVal=5

vVal is Variant
IF vVal = Null THEN ... // returns True because no value has been assigned to the variant
vVal = 0
IF vVal = Null THEN ... // returns False because the variant has been set to 0
vVal = 5
IF vVal = Null THEN ... // returns False because the variant has been set to 5

vVal is Variant
vVal = Null
IF vVal = 0 THEN ... // returns True because an unassigned variable 
// and a value cannot be compared, True is returned by convention

Type of a variant

The type of a variant is returned by the Type property. The Type property gets the type of value stored in the variable.

Remarks:

VariantConvert is used to convert the type of value stored in a Variant variable.
TypeVar is used to determine the type of variable (Variant type for a Variant variable).

vVal is Variant
TypeVar(vVal) // returns the number of the variant type
vVal..Type // returns the type of the value stored in the variant

Class property on variants

Class is used to obtain the name of the class used if the variant corresponds to a class.

Named subelements

You can directly use members without any declaration on a Variant variable.

When assigning a value to a member, if the member does not exist, it is automatically created; if the member already exits, it is modified.

Example:

Person is Variant
Person.LastName = "MOORE"
Person.FirstName = "Vince"

When reading a member, if the member does not exist, it is not created. You can check if a member exists using the Exist property.
Example:

Person is Variant
IF NOT Personn.Name..Exist THEN
Error("The name was not specified")
END

If the member does not exist, the returned value is Null. Multiple methods can be used to test the Null value:

use the Value property.
Example:
Element is Variant
IF Element.MemberNotFound..Value = Null THEN
...
END
test the Null value directly. Example:
Element is Variant
IF Element.MemberNotFound = Null THEN
...
END

Named subelements can be manipulated using the following properties:


Exist	Returns: True if the element exists, False if the element does not exist. The element is not created.
Name	Element name
Type	Type of element (same values as TypeVar).
Value	Element value.

Using the Member property on Variant variables allows you to get the array of named elements. This array can be handled by FOR EACH, the Count property, the [ ] operator, ...
It is also possible to delete an element. Example:

o is JSON
o.m = 1
o.n = 2
Trace(o)

x is Variant = o
Delete(x..Member, 1)
Trace(x) // The member has been deleted.

Indexed subelements

The Variant variable can be directly used as a Variant array. Using the [ ] operator automatically creates the array.

Example:

Days is Variant
Days[1] = "Monday"
Days[2] = "Tuesday"
Days[3] = "Wednesday"
Days[4] = "Thursday"
Days[5] = "Friday"
Days[6] = "Saturday"
Days[7] = "Sunday"

The array operations can be directly performed on the Variant variable: FOR EACH, Count, [ ] operator, etc.

Nesting named and indexed subelements

Since the named and indexed sub-elements are of type Variant, they can be nested recursively.

Example:

Library is Variant
Library.Book[1].Title = "Mrs Dalloway"
Library.Book[1].Author = "Virginia Woolf"
Library.Book[2].Title = "Oliver Twist"
Library.Book[2].Author = "Charles Dickens"