Module: Mongo::GridExt::InstanceMethods

Included in:
Mongo::Grid, Mongo::GridFileSystem
Defined in:
lib/mongo/gridfs/grid_ext.rb

Instance Method Summary collapse

Instance Method Details

#exist?(selector) ⇒ nil, Hash

Check the existence of a file matching the given query selector.

Note that this method can be used with both the Grid and GridFileSystem classes. Also keep in mind that if you’re going to be performing lots of existence checks, you should keep an instance of Grid or GridFileSystem handy rather than instantiating for each existence check. Alternatively, simply keep a reference to the proper files collection and query that as needed. That’s exactly how this methods works.

Examples:


# Check for the existence of a given filename
@grid = GridFileSystem.new(@db)
@grid.exist?(:filename => 'foo.txt')

# Check for existence filename and content type
@grid = GridFileSystem.new(@db)
@grid.exist?(:filename => 'foo.txt', :content_type => 'image/jpg')

# Check for existence by _id
@grid = Grid.new(@db)
@grid.exist?(:_id => BSON::ObjectId.from_string('4bddcd24beffd95a7db9b8c8'))

# Check for existence by an arbitrary attribute.
@grid = Grid.new(@db)
@grid.exist?(:tags => {'$in' => ['nature', 'zen', 'photography']})

Parameters:

  • selector (Hash) —

    a query selector.

Returns:

  • (nil, Hash) —

    either nil for the file’s metadata as a hash.



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# File 'lib/mongo/gridfs/grid_ext.rb', line 52

def exist?(selector)
  @files.find_one(selector)
end