Dependency Injection

Dependency injection refers to passing a piece of code all of the “things” it needs to perform a given task rather than asking that code to create all of those things itself.

More concretely, imagine an R function that needs to query a database. Instead of having the function create a connection to a database, e.g.:

query_func <- function(query) {
  con <- connect_to_db()
  
  x <- DBI::dbGetQuery(con, query)
  
  x
}

We would prefer passing a connection into the function:

query_func <- function(con, query) {
  x <- DBI::dbGetQuery(con, query)
  
  x
}

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