IsValid

Description

Determines whether an object variable is instantiated -- whether its value is a valid object handle.

Syntax

IsValid ( objectvariable )

Argument

Description

objectvariable

An object variable or a variable of type Any -- typically a reference to an object that you are testing for validity


Return value

Boolean.

Returns true if objectvariable is an instantiated object. Returns false if objectvariable is not an object, or if it is an object that is not instantiated. If objectvariable is null, IsValid returns null.

Usage

Use IsValid instead of the Handle function to determine whether a window is open.

Examples

This statement determines whether the window w_emp is open and if it is not, opens it:

IF IsValid(w_emp) = FALSE THEN Open(w_emp)

This example returns -1 because the IsValid function returns false. Although the objectvariable argument is a valid string, it is not an instantiated object. The IsValid method would return true only if la_value was an instantiated object:

any la_value
 
la_value = "I'm a string"
IF NOT IsValid(la_value) THEN return -1

See also

Handle