isS4                  package:base                  R Documentation

Test for an S4 object

Description:

     Tests whether the object was created from a formally defined
     class.

Usage:

     isS4(object)

     asS4(object, value = TRUE)

Arguments:

  object: Any R object. 

   value: A single logical value; not 'NA'.

Details:

     Note that this function does not rely on the 'methods' package, so
     in particular it can be used to detect the need to 'require()'
     that package.

     You should not set the flag directly unless you really know why. 
     In the future, S4 methods may be restricted S4 objects, for
     primitive functions; then 'asS4' would allow method dispatch of S4
     methods for S3 classes. For all other purposes, an object will
     satisfy 'isS4(x)' if and only if it should.

Value:

     'isS4' always returns 'TRUE' or 'FALSE' according to whether the
     internal flag marking an S4 object has been turned on for this
     object.

     'asS4' will turn this flag on or off. But see the details.

Examples:

     isS4(pi) # FALSE
     isS4(getClass("MethodDefinition")) # TRUE

