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- Variant type and NULL
- Type of a variant
- Class property on variants
- Named sub-elements
- Indexed sub-elements
- Nesting named and indexed sub-elements
Variant (Type of variable) 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 sub-elements.
- 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.
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 that will 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 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 the variant is not assigned
vVal = 0
IF vVal = Null THEN ... // returns False because the variant is assigned
// with an integer whose value is 0
vVal = 5
IF vVal = Null THEN ... // returns False because the variant is assigned
// with an integer whose value is 5
vVal is Variant
vVal = Null
IF vVal = 0 THEN ... // returns True because a non-assigned variable
// and a value cannot be compared, True is returned by convention
The type of a variant is returned by the Type property. The Type property is used to get 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 sub-elements You can directly use members without any declaration on a Variant variable. When assigning 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
The named sub-elements can be handled by 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 sub-elements The Variant variable can be directly used as an array of variants. 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 sub-elements 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"
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