4D v13.4

Two-dimensional Arrays

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4D v13.4
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Arrays
Two-dimensional Arrays

Two-dimensional Arrays  


 

 

Each of the array declaration commands can create or resize one-dimensional or two-dimensional arrays. Example:

 ARRAY TEXT(atTopics;100;50) ` Creates a text array composed of 100 rows of 50 columns

Two-dimensional arrays are essentially language objects; you can neither display nor print them.

In the previous example:

  • atTopics is a two-dimensional array
  • atTopics{8}{5} is the 5th element (5th column...) of the 8th row
  • atTopics{20} is the 20th row and is itself a one-dimensional array
  • Size of array(atTopics) returns 100, which is the number of rows
  • Size of array(atTopics{17}) returns 50, which the number of columns for the 17th row

In the following example, a pointer to each field of each table in the database is stored in a two-dimensional array:

 C_LONGINT($vlLastTable;$vlLastField)
 C_LONGINT($vlFieldNumber)
  ` Create as many rows (empty and without columns) as there are tables
 $vlLastTable:=Get last table number
 ARRAY POINTER(<>apFields;$vlLastTable;0) `2D array with X rows and zero columns
  ` For each table
 For($vlTable;1;$vlLastTable)
    If(Is table number valid($vlTable))
       $vlLastField:=Get last field number($vlTable)
  ` Give value of elements
       $vlColumnNumber:=0
       For($vlField;1;$vlLastField)
          If(Is field number valid($vlTable;$vlField))
             $vlColumnNumber:=$vlColumnNumber+1
  `Insert a column in a row of the table underway
             INSERT IN ARRAY(<>apFields{$vlTable};$vlColumnNumber;1)
  `Assign the "cell" with the pointer
             <>apFields{$vlTable}{$vlColumnNumber}:=Field($vlTable;$vlField)
          End if
       End for
    End if
 End for

Provided that this two-dimensional array has been initialized, you can obtain the pointers to the fields for a particular table in the following way:

  ` Get the pointers to the fields for the table currently displayed at the screen:
 COPY ARRAY(◊apFields{Table(Current form table)};$apTheFieldsIamWorkingOn)
  ` Initialize Boolean and Date fields
 For($vlElem;1;Size of array($apTheFieldsIamWorkingOn))
    Case of
       :(Type($apTheFieldsIamWorkingOn{$vlElem}->)=Is Date)
          $apTheFieldsIamWorkingOn{$vlElem}->:=Current date
       :(Type($apTheFieldsIamWorkingOn{$vlElem}->)=Is Boolean)
          $apTheFieldsIamWorkingOn{$vlElem}->:=True
    End case
 End for

Note: As this example suggests, rows of a two-dimensional arrays can be the same size or different sizes.

 
PROPERTIES 

Product: 4D
Theme: Arrays

 
SEE ALSO 

Arrays