$ISOBJECT; $ISOBJECT

Returns whether the expression is an object reference (OREF).

The outline

$ISOBJECT(expr)
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parameter

• Expr CacheObjectScript expression.

describe

If expr is an object reference (OREF), $ISOBJECT returns 1. If expr is not an object reference (OREF), $ISOBJECT returns 0.

If expr is a reference to an invalid object$ISOBJECTReturns 1. Invalid objects should not occur in normal operation; For example, recompiling a class while its instance is active can result in invalid objects.

To remove object references, set the variable to an empty string (” “). Out of date% the Close ()Method cannot be used to delete object references.% the Close ()No action is performed and success completion is always returned. Do not use it when writing new code% the Close ().

parameter

expr

CacheObjectScript expression.

The sample

The following example shows the values returned by $ISOBJECT for object references and non-object references (string references in this case) :

/// d ##class(PHA.TEST.Function).ISOBJECT()
ClassMethod ISOBJECT(a)
{
	SET a="Certainly not an object."
	SET o=##class(%SQL.Statement%).New(a)WRITE! , "the objecta: $"ISOBJECT(a)
	WRITE! ," object referenceo: $"ISOBJECT(o)}Copy the code

DHC-APP>d ##class(PHA.TEST.Function).ISOBJECT() the objecta: 0 object referenceo: 1.Copy the code

The following example shows the JSON value as an object reference:

/// d ##class(PHA.TEST.Function).ISOBJECTJSON()
ClassMethod ISOBJECTJSON(a)
{
	SET a=["apple"."banana"."orange"]
	SET b={"fruit":"orange"."color":"orange"} WRITE ! ."JSON array: ",$ISOBJECT(a) WRITE ! ."JSON object: ",$ISOBJECT(b)
}
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DHC-APP> d ##class(PHA.TEST.Function).ISOBJECTJSON(a)JSON array: 1.JSON object: 1.Copy the code

The following Dynamic SQL example shows that the flow field is an OID, not an object reference. We need to use the SQL % OBJECT function to return an OBJECT reference:

/// d ##class(PHA.TEST.Function).ISOBJECTsql()
ClassMethod ISOBJECTsql(a)
{
	ZNSPACE "SAMPLES"
	SET myquery=2
	SET myquery(1)="SELECT TOP 1 Name,Notes,%OBJECT(Notes) AS NoteObj "
	SET myquery(2)="FROM Sample.Employee WHERE Notes IS NOT NULL"
	SET tStatement = ##class(%SQL.Statement%).New(a)SET qStatus = tStatement.%Prepare(.myquery)
	IF qStatus'=1 { WRITE "%Prepare failed:" DO $System.Status.DisplayError(qStatus) QUIT } SET rset = tStatement.%Execute() WHILE rset.%Next() { WRITE "Stream field oid: ",$ISOBJECT(rset.Notes),! WRITE "Stream field oref: ",$ISOBJECT(rset.NoteObj),! }}Copy the code

DHC-APP>d ##class(PHA.TEST.Function).ISOBJECTsql(a)Stream field oid: 0
Stream field oref: 1.Copy the code

The following example shows how to remove an object reference. The % Close () method does not change object references. Setting an object reference to an empty string removes the object reference:

/// d ##class(PHA.TEST.Function).ISOBJECTsql1()
ClassMethod ISOBJECTsql1(a)
{
	SET o=##class(%SQL.Statement%).New(a)WRITE! ,"objref o: $"ISOBJECT(o)
	DO o%.Close(a); thisis a no-op WRITE ! ."objref o: ",$ISOBJECT(o)
	SET o=""WRITE ! ."objref o: ",$ISOBJECT(o)
}
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DHC-APP>d ##class(PHA.TEST.Function).ISOBJECTsql1(a)objref o: 1.objref o: 1.objref o: 0
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Pay attention to

%Close() does not reclaim the object, but removes the object reference by equating it to “”.