4D v13.4

RESOLVE POINTER

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4D v13.4
RESOLVE POINTER

RESOLVE POINTER 


 

RESOLVE POINTER ( aPointer ; varName ; tableNum ; fieldNum ) 
Parameter Type   Description
aPointer  Pointer in Pointer for which to retrieve the referenced object
varName  String in Name of referenced variable or empty string
tableNum  Longint in Number of referenced table or array element or 0 or -1
fieldNum  Longint in Number of referenced field or 0

The RESOLVE POINTER command retrieves the information of the object referenced by the pointer expression aPointer and returns it into the parameters varName, tableNum, and fieldNum.

Depending on the nature of the referenced object, RESOLVE POINTER returns the following values:

Referenced objectParameters
varNametableNumfieldNum
None (NIL pointer)"" (empty string)00
VariableName of the variable-10
ArrayName of the array-10
Array elementName of the arrayElement number0
Table"" (empty string)Table number0
Field"" (empty string)Table numberField number

Notes:

  • If the value you pass in pointer is not a pointer expression, a syntax error occurs.
  • The RESOLVE POINTER command does not work with pointers to local variables. In fact, by definition several local variables with the same name could exist in different locations, so it is not possible for the command to find the correct variable.

Within a form, you create a group of 100 enterable variables called v1, v2... v100. To do so, you perform the following steps:

a. Create one enterable variable that you name v.

b. Set the properties of the object.

c. Attach the following method to that object:

 DoSomething(Self` DoSomething being a project method in your database


d. At this point, you can either duplicate the variable as many times as you need, or use the Objects on Grid feature in the Form Editor.

e. Within the DoSomething method, if you need to know the index of the variable for which the method is called, you write:

 RESOLVE POINTER($1;$vsVarName;$vlTableNum;$vlFieldNum)
 $vlVarNum:=Num(Substring($vsVarName;2))

Note that by constructing your form in this way, you write the methods for the 100 variables only once; you do not need to write DoSomething (1), DoSomething (2)...,DoSomething (100).

For debugging purposes, you need to verify that the second parameter ($2) to a method is a pointer to a table. At the beginning of this method, you write:

  ` ...
 If(◊DebugOn)
    RESOLVE POINTER($2;$vsVarName;$vlTableNum;$vlFieldNum)
    If(Not(($vlTableNum>0)&($vlFieldNum=0)&($vsVarName="")))
  ` WARNING: The pointer is not a reference to a table
       TRACE
       End
    End if
  ` ...

See example for the DRAG AND DROP PROPERTIES command.

 
PROPERTIES 

Product: 4D
Theme: Language
Number: 394

 
INDEX

Alphabetical list of commands

 
HISTORY 

Created: 4D v6

 
SEE ALSO 

DRAG AND DROP PROPERTIES
Field
Get pointer
Is a variable
Nil
Table