4D v17.4

Is nil pointer

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4D v17.4
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Is nil pointer

Is nil pointer 


 

Is nil pointer ( aPointer ) -> Function result 
Parameter Type   Description
aPointer  Pointer in Pointer to be tested
Function result  Boolean in TRUE = Nil pointer (->[]) FALSE = Valid pointer to an existing object

The Is nil pointer command returns True if the pointer you pass in aPointer is Nil (->[]). It returns False in all other cases (pointer to field, table or variable).

If you want to find out the name of the variable or the number of the field that is being pointed to, you can use the RESOLVE POINTER command.

Example  

 C_POINTER($ptr)
 ...
 If(Is nil pointer($ptr))
 End if
  // is equivalent to
 If($ptr=Null)
 End if



See also 

Is a variable
RESOLVE POINTER

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PROPERTIES 

Product: 4D
Theme: Language
Number: 315

This command can be run in preemptive processes

 
HISTORY 

Created: < 4D v6
Renamed: 4D v16 R4

 
ARTICLE USAGE

4D Language Reference ( 4D v17)
4D Language Reference ( 4D v17.1)
4D Language Reference ( 4D v17.2)
4D Language Reference ( 4D v17.3)
4D Language Reference ( 4D v17.4)