58 lines
2.1 KiB
Ruby
58 lines
2.1 KiB
Ruby
# encoding: UTF-8
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# --
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# Copyright (C) 2008-2011 10gen Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ++
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module Mongo
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module GridExt
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module InstanceMethods
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# Check the existence of a file matching the given query selector.
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#
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# Note that this method can be used with both the Grid and GridFileSystem classes. Also
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# keep in mind that if you're going to be performing lots of existence checks, you should
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# keep an instance of Grid or GridFileSystem handy rather than instantiating for each existence
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# check. Alternatively, simply keep a reference to the proper files collection and query that
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# as needed. That's exactly how this methods works.
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#
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# @param [Hash] selector a query selector.
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#
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# @example
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#
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# # Check for the existence of a given filename
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# @grid = Mongo::GridFileSystem.new(@db)
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# @grid.exist?(:filename => 'foo.txt')
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#
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# # Check for existence filename and content type
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# @grid = Mongo::GridFileSystem.new(@db)
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# @grid.exist?(:filename => 'foo.txt', :content_type => 'image/jpg')
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#
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# # Check for existence by _id
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# @grid = Mongo::Grid.new(@db)
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# @grid.exist?(:_id => BSON::ObjectId.from_string('4bddcd24beffd95a7db9b8c8'))
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#
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# # Check for existence by an arbitrary attribute.
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# @grid = Mongo::Grid.new(@db)
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# @grid.exist?(:tags => {'$in' => ['nature', 'zen', 'photography']})
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#
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# @return [nil, Hash] either nil for the file's metadata as a hash.
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def exist?(selector)
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@files.find_one(selector)
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end
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end
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end
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end
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