Type
Type ( fieldVar ) -> Function result
| Parameter | Type | Description | |
|---|---|---|---|
| fieldVar | Field, Variable | 🡒 | field or variable to be tested |
| Function result | Longint | 🡐 | Data type number |
Description
The Type command returns a numeric value that indicates the type of field or variable you have passed in the fieldVar parameter.
4D provides the following predefined constants found in the Field and Variable Types theme:
| Constant | Type | Value |
|---|---|---|
| Array 2D | Longint | 13 |
| Blob array | Longint | 31 |
| Boolean array | Longint | 22 |
| Date array | Longint | 17 |
| Integer array | Longint | 15 |
| Is alpha field | Longint | 0 |
| Is BLOB | Longint | 30 |
| Is Boolean | Longint | 6 |
| Is collection | Longint | 42 |
| Is date | Longint | 4 |
| Is integer | Longint | 8 |
| Is integer 64 bits | Longint | 25 |
| Is longint | Longint | 9 |
| Is null | Longint | 255 |
| Is object | Longint | 38 |
| Is picture | Longint | 3 |
| Is pointer | Longint | 23 |
| Is real | Longint | 1 |
| Is string var | Longint | 24 |
| Is subtable | Longint | 7 |
| Is text | Longint | 2 |
| Is time | Longint | 11 |
| Is undefined | Longint | 5 |
| Is variant | Longint | 12 |
| LongInt array | Longint | 16 |
| Object array | Longint | 39 |
| Picture array | Longint | 19 |
| Pointer array | Longint | 20 |
| Real array | Longint | 14 |
| String array | Longint | 21 |
| Text array | Longint | 18 |
| Time array | Longint | 32 |
You can apply the Type function to fields, interprocess variables, process variables, local variables, and dereferenced pointers for these types of objects. You can apply Type to the parameters ($1, $2 ... ${...}) of a project method or to the result of a function ($0).
Notes:
- You can not apply the Type function to scalar expressions such as object properties (emp.name) or collection elements (myColl[5]). To do this, you must use the Value type command.
- In compiled mode, calling Type on a method parameter ($0, $1...) declared as C_VARIANT does not return Is variant but the actual data type (same as calling Value type).
Example 1
The following project method empties some or all of the fields for the current record of the table whose a pointer is passed as parameter. It does this without deleting or changing the current record:
// EMPTY RECORD Project Method
// EMPTY RECORD ( Pointer {; Long } )
// EMPTY RECORD ( -> [Table] { ; Type Flags } )
var $1 : Pointer
var $2;$vlTypeFlags : Integer
If(Count parameters>=2)
$vlTypeFlags:=$2
Else
$vlTypeFlags:=0xFFFFFFFF
End if
For($vlField;1;Get last field number($1))
$vpField:=Field(Table($1);$vlField)
$vlFieldType:=Type($vpField->)
If($vlTypeFlags ??$vlFieldType )
Case of
:(($vlFieldType=Is alpha field)|($vlFieldType=Is text))
$vpField->:=""
:(($vlFieldType=Is real)|($vlFieldType=Is integer)|($vlFieldType=Is longint))
$vpField->:=0
:($vlFieldType=Is date)
$vpField->:=!00/00/00!
:($vlFieldType=Is time)
$vpField->:=?00:00:00?
:($vlFieldType=Is Boolean)
$vpField->:=False
:($vlFieldType=Is picture)
var $vgEmptyPicture : Picture
$vpField->:=$vgEmptyPicture
:($vlFieldType=Is subtable)
Repeat
ALL SUBRECORDS($vpField->)
DELETE SUBRECORD($vpField->)
Until(Records in subselection($vpField->)=0)
:($vlFieldType=Is BLOB)
SET BLOB SIZE($vpField->;0)
End case
End if
End for
After this project method is implemented in your database, you can write:
// Empty the whole current record of the table [Things To Do]
EMPTY RECORD(->[Things To Do])
// Empty Text, BLOB and Picture fields for the current record of the table [Things To Do]
EMPTY RECORD(->[Things To Do];0?+Is text?+Is BLOB?+Is picture)
// Empty the whole current record of the table [Things To Do] except Alphanumeric fields
EMPTY RECORD(->[Things To Do];-1?-Is alpha field)
Example 2
In certain cases, for example when writing generic code, you may need to find out whether an array is a standard independent array or the “row” of a 2D array. In this case, you can use the following code:
ptrmyArr:=->myArr{6} // Is myArr{6} the row of a 2D array?
RESOLVE POINTER(ptrmyArr;varName;tableNum;fieldNum)
If(varName#"")
$ptr:=Get pointer(varName)
$thetype:=Type($ptr->)
// If myArr{6} is the row of a 2D array, $thetype equals 13
End if
Example 3
See example for the APPEND DATA TO PASTEBOARD command.