从“package :: function”形式的字符串中获取函数

Question

There has been discussion on how to get a variable from a string. Indeed, get works for, say, the data.table function: get("data.table") returns data.table . However,

> get("data.table::data.table")
Error in get("data.table::data.table") : 
  object 'data.table::data.table' not found

Is there a way to do this that preserves the reference to the package name? Ie, I do NOT want to simply do a split on "::" and get the second half of the string.

Answer 1

You could just use the envir argument to get the function from the namespace.

get("data.table", envir = getNamespace("data.table"))

Or more simply as @joran notes, getFromNamespace() can be used.

getFromNamespace("data.table", "data.table")