Example of Using an S3 Class in a S4 Object

问题

I want to include an RODBC connection as part of S4 object. It looks like RODBC is S3. For example:

setClass(
  Class="Node",
  representation=representation(
    nodeName = "character",
    connection = "RODBC"
  )                    
)

Throws undefined slot classes. It looks like I want to use setOldClass, but I am having trouble figuring out how to use it. Assuming I do want setOldClass, How would I use setOldClass so that I can include my RODBC connection as slot to my Node class?

回答1:

Although the documentation is quite involved for this function, if all you need to do include the class in a slot it is as simple as:

setOldClass("RODBC")

setClass(
  Class="Node",
  representation=representation(
    nodeName = "character",
    connection = "RODBC"
  )                    
)

This is also what you would use for reference classes.

来源：https://stackoverflow.com/questions/9067492/example-of-using-an-s3-class-in-a-s4-object