Class: LUSI::API::Core::Lookup::LookupTable

Inherits:
Hash
  • Object
show all
Defined in:
lib/lusi_api/core/lookup.rb

Overview

Implements a caching lookup table

Direct Known Subclasses

LUSILookupTable

Instance Method Summary collapse

Constructor Details

#initialize(*args, &block) ⇒ void

Initialises a new LookupTable instance



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# File 'lib/lusi_api/core/lookup.rb', line 36

def initialize(*args, &block)

  # Initialise the superclass
  super(*args)

  # Define a default proc to look up and cache missing keys
  # Note that if a hash has a default value set, this is lost (reset to nil) when a default_proc is set,
  # so we preserve the default value here to use in the proc.
  default_value = default
  self.default_proc = Proc.new do |hash, key|
    begin
      # If the lookup succeeds, add the value to the hash and return the value.
      self[key] = get_value(key)
    rescue LookupError => e
      # Lookup failed
      if block
        # Call the block passed by the caller
        block.call(hash, key)
      else
        # Return the default value for the hash
        default_value
      end
    end
  end

end

Instance Method Details

#get_value(key) ⇒ any

Retrieves the value for a key from some data source

Parameters:

  • key (any) —

    the key to search for

Returns:

  • (any) —

    the corresponding value

Raises:



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# File 'lib/lusi_api/core/lookup.rb', line 67

def get_value(key)
  raise LookupError.new(key)
end