isS4 {base}R Documentation

Test for an S4 object


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



asS4(object, value = TRUE)


object Any R object.
value A single logical value; not NA.


Note that isS4 does not rely on the methods package, so in particular it can be used to detect the need to require() that package. (But asS4 does depend on methods.)

You should not set the flag directly unless you really know why. In the future, S4 methods may be restricted to 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.


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.


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

[Package base version 2.5.0 Index]