OB Instance of

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4D v20 R7

OB Instance of


OB Instance of ( object ; class ) -> Function result

Parameter	Type	Description
object	Object	Object whose class is to be tested
class	Object	Class to test belongship
Function result	Boolean	True if object belongs to the specified class or a child class, and false otherwise

Description

The OB Instance of command returns true if object belongs to class or to one of its child classes, and false otherwise.

If class is not a valid Class object, the error -10745 is returned.

Note: Each time a class's sources are modified, a new Class object is generated. As previously instantiated objects do not belong to the new class, OB Instance of will return false if you pass a Class object other than the one used for instantiation.

Example

You created the Polygon class:

  //Class: Polygon

 Class constructor

 C_LONGINT($1;$2)

 This.area:=$1*$2

Then, in a method, you can write:

 C_OBJECT($poly)

 C_BOOLEAN($instance)

 

 $poly:=cs.Polygon.new(4;3)

 

 $instance:=OB Instance of($poly;cs.Polygon)

  // true

 

 $instance:=OB Instance of($poly;4D.Object)

  // true 

 

 $instance:=OB Instance of($poly;cs.Circle)

  // false