\name{InjectionListener-class}
\Rdversion{1.1}
\docType{class}
\alias{InjectionListener-class}
\alias{isListener,InjectionListener-method}
\alias{receiveMessage,InjectionListener-method}

\title{Class \code{"InjectionListener"}}
\description{

This listener takes messages that match its incomming set and inject
them into another Mongo database (presumably a queue
for another service).

}
\section{Extends}{

This class implements the \code{\link{Listener}} interface.

All reference classes extend and inherit methods from \code{"\linkS4class{envRefClass}"}.

}
\section{Methods}{
  \describe{
    \item{isListener}{\code{signature(x = "InjectionListener")}: returns
    true.}
    \item{receiveMessage}{\code{signature(x = "InjectionListener")}: If
      the message is in the \code{messSet}, it saves the message to the
      database.  (See details) }
  }
}
\details{

  The database is a \code{\link[mongolite]{mongo}} collection identified
  by \code{dburi}, \code{dbname} and \code{colname} (collection within
  the database).  The \code{mess} field of the \code{\link{P4Message}}
  is checked against the applicable messages in \code{messSet}.  If it
  is there, then the message is inserted into the collection.

}
\references{

  This is an example of the observer design pattern.
  \url{https://en.wikipedia.org/wiki/Observer_pattern}. 


}
\author{Russell Almond}
\seealso{
  \code{\link{Listener}}, \code{\linkS4class{P4Message}},
  \code{\link{InjectionListener}},
  \code{\linkS4class{UpdateListener}},
  \code{\linkS4class{UpsertListener}},
  \code{\linkS4class{CaptureListener}},
  \code{\linkS4class{TableListener}},
  \code{\link[mongolite]{mongo}}
}
\examples{
\dontrun{

mess1 <- P4Message(app="default",uid="Phred",context="Down Hill",
                   sender="EIEvent",mess="New Observables",
                   details=list(trophy="gold",solvedtime=10))
ilwind <- InjectionListener(sender="EIEvent",messSet="New Observables")
receiveMessage(ilwind,mess1)

}
}
\keyword{classes}
\section{Fields}{
  \describe{
    \item{\code{sender}:}{Object of class \code{character} which is used
      as the sender field for the message.}
    \item{\code{dbname}:}{Object of class \code{character} giving the
      name of the Mongo database }
    \item{\code{dburi}:}{Object of class \code{character} giving the url
      of the Mongo database.}
    \item{\code{colname}:}{Object of class \code{character} giving the
      column of the Mongo database. }
    \item{\code{messSet}:}{A vector of class \code{character} giving the
      name of messages which are sent to the database.  Only messages
      for which \code{mess(mess)} is an element of \code{messSet} will
      be inserted.}
    \item{\code{db}:}{Object of class \code{MongoDB} giving the
      database.  Use \code{messdb()} to access this field to makes sure
      it has been set up.}
  }
}
\section{Class-Based Methods}{
  \describe{
    \item{\code{messdb()}:}{Accessor for the database collection.
      Initializes the connection if it has not been set up.}
    \item{\code{receiveMessage(mess)}:}{ Does the work of inserting the
      message.  See Details. }
    \item{\code{initialize(sender, dbname, dburi, colname, messSet,
        ...)}:}{Sets default values for fields.}
  }
}