class ActiveStorage::Analyzer

ActiveStorage::Analyzer::ImageAnalyzer for an example of a concrete subclass.
This is an abstract base class for analyzers, which extract metadata from blobs. See

def self.accept?(blob)

the analyzer can extract metadata.
Implement this method in a concrete subclass. Have it return true when given a blob from which 
def self.accept?(blob)
  false
end

def download_blob_to_tempfile(&block) #:doc:

:doc:
Downloads the blob to a tempfile on disk. Yields the tempfile. 
def download_blob_to_tempfile(&block) #:doc:
  blob.open tmpdir: tmpdir, &block
end

def initialize(blob) 

def initialize(blob)
  @blob = blob
end

def logger #:doc:

:doc: 
def logger #:doc:
  ActiveStorage.logger
end

def metadata

Override this method in a concrete subclass. Have it return a Hash of metadata. 
def metadata
  raise NotImplementedError
end

def tmpdir #:doc:

:doc: 
def tmpdir #:doc:
  Dir.tmpdir
end