Methods

DataMapper::Sweatshop::Unique

Public Instance Methods

unique(key = nil, &block) click to toggle source

Yields a value to the block. The value is unique for each invocation with the same block. Alternatively, you may provide an explicit key to identify the block.

If a block with no parameter is supplied, unique keeps track of previous invocations, and will continue yielding until a unique value is generated. If a unique value is not generated after @UniqueWorker::MAX_TRIES@, an exception is raised.

ParseTree is required unless an explicit key is provided

  (1..3).collect { unique {|x| x }}     # => [0, 1, 2]
  (1..3).collect { unique {|x| x + 1 }} # => [1, 2, 3]
  (1..3).collect { unique {|x| x }}     # => [3, 4, 5] # Continued on from above
  (1..3).collect { unique(:a) {|x| x }} # => [0, 1, 2] # Explicit key overrides block identity

  a = [1, 1, 1, 2, 2, 3]
  (1..3).collect { unique { a.shift }}  # => [1, 2, 3]
  (1..3).collect { unique { 1 }}        # raises TooManyTriesException

return the return value of the block

    # File lib/dm-sweatshop/unique.rb, line 27
27:       def unique(key = nil, &block)
28:         if block.arity < 1
29:           UniqueWorker.unique_map ||= {}
30: 
31:           key ||= UniqueWorker.key_for(&block)
32:           set = UniqueWorker.unique_map[key] || Set.new
33:           result = block[]
34:           tries = 0
35:           while set.include?(result)
36:             result = block[]
37:             tries += 1
38: 
39:             raise TooManyTriesException.new("Could not generate unique value after #{tries} attempts") if tries >= UniqueWorker::MAX_TRIES
40:           end
41:           set << result
42:           UniqueWorker.unique_map[key] = set
43:         else
44:           UniqueWorker.count_map ||= Hash.new() { 0 }
45: 
46:           key ||= UniqueWorker.key_for(&block)
47:           result = block[UniqueWorker.count_map[key]]
48:           UniqueWorker.count_map[key] += 1
49:         end
50: 
51:         result
52:       end

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