Object Info Routines - Object Info Routines The following routines provide ability obtain complete information about object whole obtain information about individual items within object see ldquoItem Info Routinesrdquo OT IsObject version OT Type Description inObject Longint handle result Longint inObject ObjectTools larr object handle not Discussion To test whether given Longint value valid object handle use OT IsObject inObject points valid object returned inObject zero points some other type object zero returned While possible construct BLOB would fool ObjectTools thinking was object extremely unlikely All ObjectTools methods check validity object handle passed prevent truly nasty things from happening Unless unsure about contents variable passed ObjectTools object handle need call OT IsObject Example If try retrieve embedded object from another object does not exist null object handle returned case would test result shown example below tagquot If OK1 amp GetObject tag not valid OT IsObject Do something object End ifEnd ifThe above example assumes requested tag valid tries get embedded object before checking tagrsquos validity Another approach would check tag using OT ItemExists See OT ItemExists OT ItemCount version OT inTag Number Type Description inObject Longint handle String Tag embedded object result Number item count larr Discussion OT ItemCount returns number top level items referenced object Items embedded objects not included count If inObject not valid object handle error generated OK set zero zero returned If tag not passed empty count top level items object returned If tag passed not empty valid item reference embedded object count top level items embedded object returned Otherwise error generated OK set zero zero returned See OT IsObject OT IsEmbedded OT ObjectSize version OT Number Type Description inObject Longint handle result Number total size object byteslarr Discussion OT ObjectSize returns total size object memory inObject not valid object handle error generated OK set zero zero returned See OT

Object Info Routines

The following routines provide the ability to obtain complete information about an object as a whole. To obtain information about individual items within an object, see “Item Info Routines”

OT IsObject version 1

OT IsObject(inObject) Longint

→

Parameter Type Description

inObject Longint A handle to an object

→

Function result Longint 1 if inObject is an ObjectTools ← object handle, 0 if not

Discussion

To test whether a given Longint value is a valid object handle, use OT IsObject. If inObject points to a valid object, 1 is returned. If inObject is zero or points to some other type of object, zero is returned.

While it is possible to construct a BLOB that would fool ObjectTools into thinking it was a object, this is extremely unlikely.

All ObjectTools methods check the validity of the object handle passed in to prevent truly nasty things from happening. Unless you are unsure about the contents of a variable or ﬁeld passed to ObjectTools as a object handle, there is no need to call OT IsObject ﬁrst.

Example

If you try to retrieve an embedded object from another object and it does not exist, a null object handle is returned. In that case you would want to test the result as shown in the example below.

C_STRING(255;$tag)

$tag:=Request("Item tag:")

If ((OK=1) & (Length($tag)>0)

C_LONGINT($embedded)

$embedded:=OT GetObject (stMyObject;$tag) `$tag may not be valid!

If (OT IsObject ($embedded)) `Do something with the object End ifEnd if

The above example assumes that the requested tag is valid and tries to get the embedded object before checking the tag’s validity. Another approach would be to check the tag ﬁrst by using OT ItemExists.