Type Predicates | Shrine (original) (raw)

The type_predicates plugin adds predicate methods toShrine::UploadedFile based on the MIME type. By default, it uses theMiniMime gem for looking up MIME types.

# Gemfile
gem "mini_mime"
Shrine.plugin :type_predicates

General predicates​

The plugin adds four predicate methods based on the general type of the file:

file.image? # returns true for any "image/*" MIME type
file.video? # returns true for any "video/*" MIME type
file.audio? # returns true for any "audio/*" MIME type
file.text?  # returns true for any "text/*" MIME type

If mime_type metadata value is nil, Shrine::Error will be raised.

Specific predicates​

The UploadedFile#type? method takes a file extension, and returns whether themime_type metadata value of the uploaded file matches the MIME type associated to the given file extension.

file.type?(:jpg) # returns true if MIME type is "image/jpeg"
file.type?(:svg) # returns true if MIME type is "image/svg+xml"
file.type?(:mov) # returns true if MIME type is "video/quicktime"
file.type?(:ppt) # returns true if MIME type is "application/vnd.ms-powerpoint"
...

For convenience, you can create predicate methods for specific file types:

Shrine.plugin :type_predicates, methods: %i[jpg svg mov ppt]
file.jpg? # returns true if MIME type is "image/jpeg"
file.svg? # returns true if MIME type is "image/svg+xml"
file.mov? # returns true if MIME type is "video/quicktime"
file.ppt? # returns true if MIME type is "application/vnd.ms-powerpoint"

If mime_type metadata value is nil, or the underlying MIME type library doesn't recognize a given type, Shrine::Error will be raised.

MIME database​

The MIME type lookup by file extension is done by the underlying MIME type library (MiniMime by default). You can change the MIME type library via the:mime plugin option:

Shrine.plugin :type_predicates, mime: :marcel # requires adding "marcel" gem to the Gemfile

The following MIME type libraries are supported:

Name Description
:mini_mime (Default.) Uses MiniMime gem to look up MIME type by extension.
:mime_types Uses mime-types gem to look up MIME type by extension.
:mimemagic Uses MimeMagic gem to look up MIME type by extension.
:marcel Uses Marcel gem to look up MIME type by extension.
:rack_mime Uses Rack::Mime to look up MIME type by extension.

You can also specify a custom block, which receives the extension and is expected to return the corresponding MIME type. Inside the block you can call into existing MIME type libraries:

Shrine.plugin :type_predicates, mime: -> (extension) do
  mime_type   = Shrine.type_lookup(extension, :marcel)
  mime_type ||= Shrine.type_lookup(extension, :mini_mime)
  mime_type
end