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Contents
require 'util/json_store'
# An hash that is automatically persisted to a JSON file.
# This class behaves *similarly* to a regular Hash but it persists every operation
# to a specified JSON file.
# Not all Hash operations are supported and we added some of our own.
class JSONFilePersistedHash
def initialize( file )
@store = JSONStore.new(file, true)
end
# Methods borrowed from Ruby's Hash class
def []( key )
@store.transaction { @store[key] }
end
def []=( key, val )
@store.transaction { @store[key]=val }
end
def delete( key )
@store.transaction { @store.delete key }
end
def empty?
@store.transaction { @store.to_h.empty? }
end
def has_key?( key )
@store.transaction { @store.to_h.has_key? key }
end
def include?( key )
has_key? key
end
def to_s
@store.transaction { @store.to_h.to_s }
end
def to_h
@store.transaction { @store.to_h }
end
def keys
@store.transaction { @store.to_h.keys }
end
def length
@store.transaction { @store.to_h.length }
end
# PersistedHash-only public methods
# Adds a <key, value> pair to the PersistedHash _only if_
# there is currently no value associated with the specified key.
# @return [Boolean] false if the key already exists, true if the
# <key, value> pair was added successfully
def add_key_value?(key, val)
@store.transaction do
return false if @store.to_h.key? key
@store[key]=val
end
true
end
# Removes a <key, value> pair from the PersistedHash _only if_
# there is currently a value associated with the specified key.
# @return [Boolean] false if there is no value associated with
# the specified key, true otherwise
def delete_key_value?( key )
@store.transaction { return false if @store.delete(key).nil? }
true
end
end
Version data entries
13 entries across 13 versions & 1 rubygems