Save objects to disk

Generic to save assorted R objects into appropriate on-disk representations. More methods may be defined by other packages to extend the alabaster.base framework to new classes.

saveObject(x, path, ...)

Arguments

x

A Bioconductor object of the specified class.

path

String containing the path to a directory in which to save x.

...

Additional named arguments to pass to specific methods.

Value

dir is created and populated with files containing the contents of x. NULL should be invisibly returned.

Comments for extension developers

Methods for the saveObject generic should create a directory at path in which the contents of x are to be saved. The files may consist of any format, though language-agnostic formats like HDF5, CSV, JSON are preferred. For more complex objects, multiple files and subdirectories may be created within path. The only strict requirements are:

• There must be an OBJECT file inside path, containing a JSON object with a "type" string property that specifies the class of the object, e.g., "data_frame", "summarized_experiment". This will be used by loading functions to determine how to load the files into memory.

• The names of files and subdirectories should not start with _ or .. These are reserved for applications, e.g., to build manifests or to store additional metadata.

Callers can pass optional parameters to specific saveObject methods via .... Any options recognized by a method should be prefixed by the name of the class used in the method's signature, e.g., any options for saveObject,DataFrame-method should start with DataFrame.. This scoping avoids conflicts between otherwise identically-named options of different methods.

When developing saveObject methods of complex objects, a simple approach is to decompose x into its “child” components. Each component can then be saved into a subdirectory of path, levering the existing saveObject methods for the component classes. In such cases, extension developers should actually call altSaveObject on each child component, rather than calling saveObject directly. This ensures that any application-level overrides of the loading functions are respected. It is expected that each method will forward ... (possibly after modification) to any internal altSaveObject calls.

Comments for application developers

Application developers can override saveObject by specifying a custom function in altSaveObject. This can be used to point to a different function to handle the saving process for each class. The custom function can be as simple as a wrapper around saveObject with some additional actions (e.g., to save more metadata), or may be as complex as a full-fledged generic with its own methods for class-specific customizations.

Author

Aaron Lun

Examples

library(S4Vectors)
X <- DataFrame(X=LETTERS, Y=sample(3, 26, replace=TRUE))

tmp <- tempfile()
saveObject(X, tmp)
list.files(tmp, recursive=TRUE)
#> [1] "OBJECT"           "basic_columns.h5"