Fetch Handle (Materialize Download)

Materializes a lazy handle by downloading the referenced dataset. If the handle is already in "ready" state, returns it unchanged unless force = TRUE.

Usage

on_fetch(handle, ...)

# S3 method for class 'openneuro_handle'
on_fetch(handle, quiet = FALSE, force = FALSE, ...)

Arguments

handle

An object to fetch. For openneuro_handle objects, triggers the download.

...

Additional arguments passed to methods.

quiet

If TRUE, suppress progress output during download.

force

If TRUE, re-download even if handle is already "ready".

Value

The handle with updated state. For openneuro_handle, returns the handle with state = "ready", path set to the download location, and fetch_time set to current time.

Important

You must capture the return value! S3 objects have copy semantics:

# CORRECT
handle <- on_fetch(handle)

# WRONG - changes are lost
on_fetch(handle)

See also

on_handle() to create a handle, on_path() to get path.

Examples

if (FALSE) { # \dontrun{
handle <- on_handle("ds000001", files = "participants.tsv")
handle <- on_fetch(handle)  # Downloads now
handle$state  # "ready"
} # }