#31 no more default parallel handler, download examples

R/ZenodoRecord.R

@@ -332,13 +332,13 @@
 #'    download directory (by default it will be the current working directory).
 #'    
 #'    The argument \code{parallel} (default is \code{FALSE}) can be used to parallelize
-#'    the files download. If set to \code{TRUE}, files will be downloaded in parallel
-#'    using default \code{mclapply} interface from \pkg{parallel} package. To use a different
-#'    parallel handler (such as eg \code{parLapply} or \code{parSapply}), specify its function
+#'    the files download. If set to \code{TRUE}, files will be downloaded in parallel.
+#'    using the chosen \code{parallel_handler}, eg \code{mclapply} interface from \pkg{parallel} package. 
+#'    To use a different parallel handler (such as eg \code{parLapply} or \code{parSapply}), specify its function
 #'    in \code{parallel_handler} argument. For cluster-based parallel download, this is the 
 #'    way to proceed. In that case, the cluster should be created earlier by the user with 
 #'    \code{makeCluster} and passed as \code{cl} argument. After downloading all files, the cluster
-#'    will be stopped automatically.
+#'    will be stopped automatically. See examples in \code{download_zenodo} utility function.
 #'    
 #'    The logical argument \code{quiet} (default is \code{FALSE}) can be set to 
 #'    suppress informative messages (not warnings).
@@ -1187,20 +1187,22 @@ ZenodoRecord <-  R6Class("ZenodoRecord",
 
         if(parallel){
           if (!quiet) self$INFO("Download in parallel mode")
-          if(is.null(parallel_handler)){
-            if (!quiet) self$INFO("Using default parallel 'mclapply' handler")
-            if (!quiet) self$INFO(files_summary)
-            invisible(mclapply(self$files, download_file, ...))
-          }else{
-            if (!quiet) self$INFO("Using cluster-based parallel handler")
-            if(is.null(cl)){
-              errMsg <- "No cluster object defined as 'cl' argument. Aborting file download..."
-              self$ERROR(errMsg)
-              stop(errMsg)
+          if (is.null(parallel_handler)) {
+            errMsg <- "No 'parallel_handler' specified"
+            self$ERROR(errMsg)
+            stop(errMsg)
+          }
+          if(!is.null(parallel_handler)){
+            if(!is.null(cl)){
+              if (!quiet) self$INFO("Using cluster-based parallel handler (cluster 'cl' argument specified)")
+              if (!quiet) self$INFO(files_summary)
+              invisible(parallel_handler(cl, self$files, download_file, ...))
+              try(stopCluster(cl))
+            }else{
+              if (!quiet) self$INFO("Using non cluster-based (no cluster 'cl' argument specified)")
+              if (!quiet) self$INFO(files_summary)
+              invisible(parallel_handler(self$files, download_file, ...))
             }
-            if (!quiet) self$INFO(files_summary)
-            invisible(parallel_handler(cl, self$files, download_file, ...))
-            try(stopCluster(cl))
           }
         }else{
           if (!quiet) self$INFO("Download in sequential mode")

R/zen4R_downloader.R

@@ -6,7 +6,14 @@
 #'
 #' @examples 
 #' \dontrun{
-#' download_zenodo("10.5281/zenodo.2547036")
+#'  #simple download (sequential)   
+#'  download_zenodo("10.5281/zenodo.2547036")
+#'  
+#'  #download files as parallel using a cluster approach (for both Unix/Win systems)
+#'  download_zenodo("10.5281/zenodo.2547036", parallel = TRUE, parallel_handler = parLapply, cl = makeCluster(2))
+#'  
+#'  #download files as parallel using mclapply (for Unix systems)
+#'  download_zenodo("10.5281/zenodo.2547036", parallel = TRUE, parallel_handler = mclapply, mc.cores = 2)
 #' }
 #'                 
 #' @param doi a Zenodo DOI or concept DOI