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CLEAR Function

Microsoft Dynamics Nav 2009

Clears the value of a single variable. Also clears all the filters that were set if the variable is a record and resets the key to the primary key.


CLEAR(Variable)

Parameters

Variable

Type: Any

The identifier (variable) of any C/AL data type, including simple and composite data types. The following rules apply when you run the CLEAR function:

  • A number variable is set to 0 (zero)

  • A string variable is set to empty string

  • A date variable is set to 0D (undefined date)

  • A time variable is set to 0T (undefined time)

  • A Boolean variable is set to FALSE

Use the CLEARALL Function to clear all internal variables, keys, and filters in the object and in any associated objects such as reports, forms, and codeunits that contain C/AL code. Note, however, that CLEARALL does not affect or change values for variables in single instance codeunits.

For a composite data type, such as a record or an array, all elements are cleared. Furthermore, all fields in a record will be initialized with the InitValue Property of the field.

CLEAR can also be used on the GUID Data Type. It converts the GUID to zeros. Use the CREATEGUID function to create a new unique GUID.

For an Automation object, CLEAR releases the Automation object and decreases the reference count. The Automation server determines if this should cause a shutdown. After CLEAR, you can use the CREATE Function (Automation) on the Automation variable to create a new instance of the object.

If you use CLEAR on a codeunit, only the reference to the codeunit is deleted and not the codeunit itself, as with Automation objects. This means that the content of the codeunit stays intact.

If you have an array of controls, the whole array is destroyed when the array variable goes out of scope.

If you have an array of automation servers, you may CLEAR the whole array at once, or CLEAR each element individually.

This example shows how to use the CLEAR function.

This example requires that you create the following text constants in the C/AL Globals window

Text constant ENU value

Text000

'Joe Raybon'

Text001

'Initially the variable "Name" contains: >%1<'

Text002

'After using CLEAR, the variable "Name" contains: >%1<'

Name := Text000;
MESSAGE(Text001, Name);
CLEAR(Name);
MESSAGE(Text002, Name);

The first message window displays the following:

Initially the variable "Name" contains: >Joe Raybon<

The second message window displays the following:

After using CLEAR, the variable "Name" contains: ><

In the following example you will declare two variables:

MyTextVar, data type: "text".
GuidVar, data type: "GUID".

These variables will be declared and cleared, first by using CLEAR and then by using CLEARALL.

This example requires that you create the following text constants in the C/AL Globals window

Text constant ENU value

Text000

My Text

Text001

Initially the variable "MyTextVar" contains >%1< and "GuidVar" is defined as >%2<

Text002

After using CLEAR(MyTextVar), the variable "MyTextVar" contains >%1< and "GuidVar" is still defined as >%2<

Text003

After using CLEAR(GuidVar) the variable "GuidVar" becomes undefined

Text004

Giving the "MyTextVar" variable the initial value again and creating a new "GuidVar" results in >%1< and >%2<

Text005

Using CLEARALL results in an empty "MyTextVar" >%1< and an undefined "GuidVar"

MyTextVar := Text000;
GuidVar := CREATEGUID();
MESSAGE(Text001,MyTextVar,GuidVar);
CLEAR(MyTextVar);
MESSAGE(Text002,MyTextVar,GuidVar);
CLEAR(GuidVar);
MESSAGE(Text003,GuidVar);
MyTextVar := Text000;
GuidVar := CREATEGUID();
MESSAGE(Text004,MyTextVar,GuidVar);
CLEARALL;
MESSAGE(Text005,MyTextVar,GuidVar);

The first message window displays the following:

Initially the variable "MyTextVar" contains: >My Text< and "GuidVar" is defined as >12345678-1234-1234-1234-1234567890AB<

The second message window displays the following:

After using CLEAR(MyTextVar), the variable "MyTextVar" contains: >< and GuidVar is still defined as >12345678-1234-1234-1234-1234567890AB<

The third message window displays the following:

After using CLEAR(GuidVar) the variable "GuidVar" becomes undefined

The fourth message window displays the following:

Giving the "MyTextVar" variable the initial value again and creating a new "GuidVar" results in >My Text< and >87654321-4321-4321-4321-BA0987654321<

The fifth message window displays the following:

Using CLEARALL results in an empty "MyTextVar" >< and an undefined "GuidVar"

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