EMPTY( ) Function
Determines whether an expression evaluates to empty.
EMPTY(eExpression)
Return Values
Logical
Parameters
eExpression
Specifies the expression that EMPTY( ) evaluates.The expression you include can be a character, numeric, date, or logical expression, or the name of a memo or general field in an open table. EMPTY( ) returns true (.T.) when expressions evaluate to the following:
Expression type Evaluates to Character The empty string, spaces, tabs, carriage returns, linefeeds, or any combination of these. Numeric 0 Currency 0 Float 0 Integer 0 Double 0 Date Empty (e.g. CTOD('')) DateTime Empty (e.g. CTOT('')) Logical False (.F.) Memo Empty (no contents) General Empty (no OLE object) Picture Empty (no picture) EMPTY( ) cannot be used to determine if a variable object reference is empty. For example, a variable can contain an object reference for a form. If the form is closed by clicking Close from the form's pop-up menu or by issuing CLEAR WINDOWS, the variable contains the null value.
The following program example demonstrates how to use TYPE( ) and ISNULL( ) to determine if a variable object reference is valid.
goMyForm = CREATEOBJECT('Form') WAIT WINDOW IIF(TYPE('goMyForm') = 'O' AND !ISNULL(goMyForm), ; 'goMyForm has valid object reference',; 'goMyForm does not have valid object reference')
Remarks
EMPTY( ) returns true (.T.) if the expression eExpression evaluates to empty; otherwise, EMPTY( ) returns false (.F.).
Example
The following example opens the customer table in the testdata database. FOR ... ENDFOR is used to create a loop in which EMPTY( ) s used to determine if TAG( ) returns the empty string. The name of each structural index tag is displayed with its candidate status.
CLOSE DATABASES
OPEN DATABASE (HOME(2) + 'data\testdata')
USE customer && Open customer table
FOR nCount = 1 TO 254
IF !EMPTY(TAG(nCount)) && Checks for empty string
? TAG(nCount) && Display tag name
? CANDIDATE(nCount) && Display candidate status
ELSE
EXIT && Exit the loop when no more tags are found
ENDIF
ENDFOR