R/fredAPI.R

In n0Trader/TDI: R Trading Data Interface

#' @title FRED economic date API (R6 constructor class)
#' @description
#' FRED economic data API inherits `TDIConnection` to implement the FRED API requests.
#' @seealso API documentation on \strong{\href{https://research.stlouisfed.org/docs/api/}{St. Louis Fed web services website}}.
#' @import R6
#' @export
fredAPI <- R6::R6Class("fredAPI", inherit = TDIConnection,
  cloneable = FALSE, class = TRUE, # enabled S3 classes

  # Implement API driver endpoints.
  public = list(
    #' @description
    #' Retrieve historical prices for the symbol.
    #' @param ... see \code{\link{TDIConnection}}
    #' @return An object of class `Instrument` with historical prices.
    getChart = function(...) {
      args <- super$getChart(...)

      # Try to execute the Json API request.
      tryCatch({
        query <- list(file_type = "json",
          series_id = args$symbol,
          api_key = as.character(self$conn_args$api_key)
        )
        res <- private$requestString(
          endpoint = "chart",
          query = query
        ) %>% private$jsonRequest()

        return(res)

      }, error = function(e) {
        msg <- conditionMessage(e)
        warning(msg, call. = TRUE)
      })
    }
  )
)