Add support for mesh files in MSH format

class to represent MSH mesh files

Closes #67 (closed)

R/ogs6_msh.R

+#' OGS6_msh
+#' @description Small class to support \code{MSH} mesh files. Note that
+#' MSH files are a legacy format from OGS5. It is recommended to switch to VTU
+#'  files.
+#' @export
+OGS6_msh <- R6::R6Class("OGS6_msh",
+    public = list(
+        #' @description reates new OGS6_vtu object..
+        #' @param msh_path path to \code{*.msh} file.
+        initialize = function(msh_path) {
+
+            assertthat::is.string(msh_path)
+            assertthat::assert_that(file.exists(msh_path))
+            private$.msh_path <- msh_path
+        },
+        #' @description Overrides the default print method
+        print = function(){
+            cat("OGS6_msh\n")
+            cat("msh path:\n")
+            cat(private$.msh_path, "\n\n")
+            invisible(self)
+        }
+    ),
+    # === active fields
+
+    active = list(
+        #' @field msh_path
+        #' Getter/setter for private parameter `.msh_path`
+        msh_path = function(value) {
+            if (missing(value)) {
+                private$.msh_path
+            } else {
+                assertthat::assert_that(assertthat::is.string(value))
+                private$.msh_path <- value
+            }
+        }
+    ),
+    private = list(
+        .msh_path = NULL
+    )
+)
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