Class: HashCabinet

Inherits:
Object
  • Object
show all
Defined in:
lib/hash_cabinet.rb

Defined Under Namespace

Modules: Refinements

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(path) ⇒ HashCabinet

Initializes a new database file at #path

Parameters:

  • path (String) —

    the path to the database file



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# File 'lib/hash_cabinet.rb', line 30

def initialize(path)
  @path = path
end

Instance Attribute Details

#path ⇒ String (readonly)

Returns the path to the database file.

Returns:

  • (String) —

    the path to the database file



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# File 'lib/hash_cabinet.rb', line 6

class HashCabinet

  # Refinements for internal use
  module Refinements
    refine String do
      def from_yaml
        YAML.load self
      end
    end

    refine NilClass do
      def from_yaml
        nil
      end
    end
  end

  using Refinements

  attr_reader :path

  # Initializes a new database file at {path}
  #
  # @param [String] path the path to the database file
  def initialize(path)
    @path = path
  end

  # Yields the +SDBM+ object to the block. 
  #
  # @example
  #   cabinet = HashCabinet.new 'filename'
  #
  #   cabinet.transaction do |db|
  #     db.clear
  #   end
  #
  # @note 
  #   Under most circumstances, this method should not be used directly, 
  #   as it is used by all other methods.
  #
  # @yieldparam [SDBM] db the {SDBM} instance
  def transaction(&block)
    SDBM.open path, &block
  end

  # @return [Object] the value in the database associated with the given +key+.
  def [](key)
    transaction { |db| db[key.to_s].from_yaml }
  end

  # Inserts or updates a value in the database with the given key as an index.
  def []=(key, value)
    transaction { |db| db[key.to_s] = value.to_yaml }
  end

  # Deletes all key-value pairs from the database.
  def clear
    transaction { |db| db.clear }
  end

  # Deletes the given `key` from the database.
  def delete(key)
    transaction { |db| db.delete key.to_s }
  end

  # Iterates over the key-value pairs in the database, deleting those for
  # which the block returns true.
  # 
  # @example Delete all records with +age < 18+.
  #   cabinet = HashCabinet.new 'filename'
  #
  #   cabinet.delete_if do |key, value|
  #     value[:age] < 18
  #   end
  #
  # @yieldparam [String] key the pair key
  # @yieldparam [Object] value the pair value
  def delete_if(&block)
    transaction do |db|
      db.delete_if do |key, value|
        yield key, value.from_yaml
      end
    end
  end

  # Iterates over each key-value pair in the database.
  #
  # @yieldparam [String] key the pair key
  # @yieldparam [Object] value the pair value
  def each(&block)
    transaction do |db|
      db.each do |key, value|
        yield key, value.from_yaml
      end
    end
  end
  
  # Iterates over each key in the database.
  #
  # @yieldparam [String] key the pair key
  def each_key(&block)
    transaction { |db| db.each_key(&block) }
  end
  
  # Iterates over each key-value pair in the database.
  #
  # @yieldparam [Object] value the pair value
  def each_value(&block)
    transaction do |db|
      db.each_value do |value|
        yield value.from_yaml
      end
    end
  end

  # @return [Boolean] +true+ if the database is empty.
  def empty?
    transaction { |db| db.empty? }
  end

  # @return [Boolean] +true+ if the database contains the given key.
  def has_key?(key)
    transaction { |db| db.has_key? key.to_s }
  end
  alias include? has_key?
  alias key? has_key?

  # @return [Boolean] +true+ if the database contains the given value.
  def has_value?(value)
    transaction { |db| db.has_value? value.to_yaml }
  end

  # Returns the key associated with the given value.
  #
  # If more than one key corresponds to the given value, then the first key will be returned.
  # If no keys are found, +nil+ will be returned.
  #
  # @return [String] the key associated with the given value. 
  def key(value)
    transaction { |db| db.key value.to_yaml }
  end

  # @return [Array] a new Array containing the keys in the database.
  def keys
    transaction { |db| db.keys }
  end

  # @return [Integer] the number of keys in the database.
  def length
    transaction { |db| db.length }
  end
  alias size length
  alias count length

  # Empties the database, then inserts the given key-value pairs.
  #
  # This method will work with any object which implements an +#each_pair+
  # method, such as a Hash, or with any object that implements an +#each+
  # method, such as an Array. In this case, the array will be converted to 
  # a `key=key` hash before storing it.
  # 
  # @example
  #   cabinet = HashCabinet.new 'filename'
  #   cabinet.replace key1: 'value1', key2: 'value2'
  #
  # @param [Object] data the data to store
  def replace(data)
    if !data.respond_to? :each_pair and data.respond_to? :each
      data = array_to_hash data
    end

    data = normalize_types data
    transaction { |db| db.replace data }
  end

  # @return [Hash] a new Hash of key-value pairs for which the block returns true.
  def select(&block)
    transaction do |db|
      db.select do |key, value|
        yield key, value.from_yaml
      end.to_h.transform_values &:from_yaml
    end
  end

  # Removes a key-value pair from the database and returns them as an Array.
  #
  # If the database is empty, returns nil.
  #
  # @return [Array] the key and value.
  def shift
    transaction do |db| 
      result = db.shift
      [result[0], result[1].from_yaml]
    end
  end

  # @return [Array] a new array containing each key-value pair in the 
  #   database.
  def to_a
    transaction do |db| 
      db.to_a.map { |pair| [pair[0], pair[1].from_yaml] }
    end
  end

  # @return [hash] a new hash containing each key-value pair in the database.
  def to_h
    transaction do |db| 
      db.to_h.transform_values &:from_yaml
    end
  end

  # Inserts or updates key-value pairs.
  # 
  # This method will work with any object which implements an +#each_pair+
  # method, such as a Hash, or with any object that implements an +#each+
  # method, such as an Array. In this case, the array will be converted to 
  # a `key=key` hash before storing it.
  #
  # @example
  #   cabinet = HashCabinet.new 'filename'
  #   cabinet.update key1: 'value1', key2: 'value2'
  #
  # @param [Object] data the data to store
  def update(data)
    if !data.respond_to? :each_pair and data.respond_to? :each
      data = array_to_hash data
    end

    data = normalize_types data
    transaction { |db| db.update data }
  end

  # @return [Boolean] +true+ if the database contains the given value.
  def value?(value)
    transaction { |db| db.value? value.to_yaml }
  end

  # @return [Array] a new array containing the values in the database.
  def values
    transaction do |db| 
      db.values.map &:from_yaml
    end
  end

  # @return [Array] an Array of values corresponding to the given keys.
  def values_at(*key)
    transaction do |db| 
      db.values_at(*(key.map &:to_s)).map &:from_yaml
    end
  end

private

  def array_to_hash(array)
    array.map { |item| [item, item] }.to_h
  end

  def normalize_types(hash)
    hash.map do |key, value|
      [key.to_s, value.to_yaml]
    end.to_h
  end

end

Instance Method Details

#[](key) ⇒ Object

Returns the value in the database associated with the given key.

Returns:

  • (Object) —

    the value in the database associated with the given key.



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# File 'lib/hash_cabinet.rb', line 53

def [](key)
  transaction { |db| db[key.to_s].from_yaml }
end

#[]=(key, value) ⇒ Object

Inserts or updates a value in the database with the given key as an index.



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# File 'lib/hash_cabinet.rb', line 58

def []=(key, value)
  transaction { |db| db[key.to_s] = value.to_yaml }
end

#clear ⇒ Object

Deletes all key-value pairs from the database.



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# File 'lib/hash_cabinet.rb', line 63

def clear
  transaction { |db| db.clear }
end

#delete(key) ⇒ Object

Deletes the given ‘key` from the database.



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# File 'lib/hash_cabinet.rb', line 68

def delete(key)
  transaction { |db| db.delete key.to_s }
end

#delete_if {|key, value| ... } ⇒ Object

Iterates over the key-value pairs in the database, deleting those for which the block returns true.

Examples:

Delete all records with age < 18.

cabinet = HashCabinet.new 'filename'

cabinet.delete_if do |key, value|
  value[:age] < 18
end

Yield Parameters:

  • key (String) —

    the pair key

  • value (Object) —

    the pair value



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# File 'lib/hash_cabinet.rb', line 84

def delete_if(&block)
  transaction do |db|
    db.delete_if do |key, value|
      yield key, value.from_yaml
    end
  end
end

#each {|key, value| ... } ⇒ Object

Iterates over each key-value pair in the database.

Yield Parameters:

  • key (String) —

    the pair key

  • value (Object) —

    the pair value



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# File 'lib/hash_cabinet.rb', line 96

def each(&block)
  transaction do |db|
    db.each do |key, value|
      yield key, value.from_yaml
    end
  end
end

#each_key {|key| ... } ⇒ Object

Iterates over each key in the database.

Yield Parameters:

  • key (String) —

    the pair key



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# File 'lib/hash_cabinet.rb', line 107

def each_key(&block)
  transaction { |db| db.each_key(&block) }
end

#each_value {|value| ... } ⇒ Object

Iterates over each key-value pair in the database.

Yield Parameters:

  • value (Object) —

    the pair value



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# File 'lib/hash_cabinet.rb', line 114

def each_value(&block)
  transaction do |db|
    db.each_value do |value|
      yield value.from_yaml
    end
  end
end

#empty? ⇒ Boolean

Returns true if the database is empty.

Returns:

  • (Boolean) —

    true if the database is empty.



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# File 'lib/hash_cabinet.rb', line 123

def empty?
  transaction { |db| db.empty? }
end

#has_key?(key) ⇒ Boolean Also known as: include?, key?

Returns true if the database contains the given key.

Returns:

  • (Boolean) —

    true if the database contains the given key.



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# File 'lib/hash_cabinet.rb', line 128

def has_key?(key)
  transaction { |db| db.has_key? key.to_s }
end

#has_value?(value) ⇒ Boolean

Returns true if the database contains the given value.

Returns:

  • (Boolean) —

    true if the database contains the given value.



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# File 'lib/hash_cabinet.rb', line 135

def has_value?(value)
  transaction { |db| db.has_value? value.to_yaml }
end

#key(value) ⇒ String

Returns the key associated with the given value.

If more than one key corresponds to the given value, then the first key will be returned. If no keys are found, nil will be returned.

Returns:

  • (String) —

    the key associated with the given value.



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# File 'lib/hash_cabinet.rb', line 145

def key(value)
  transaction { |db| db.key value.to_yaml }
end

#keys ⇒ Array

Returns a new Array containing the keys in the database.

Returns:

  • (Array) —

    a new Array containing the keys in the database.



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# File 'lib/hash_cabinet.rb', line 150

def keys
  transaction { |db| db.keys }
end

#length ⇒ Integer Also known as: size, count

Returns the number of keys in the database.

Returns:

  • (Integer) —

    the number of keys in the database.



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# File 'lib/hash_cabinet.rb', line 155

def length
  transaction { |db| db.length }
end

#replace(data) ⇒ Object

Empties the database, then inserts the given key-value pairs.

This method will work with any object which implements an #each_pair method, such as a Hash, or with any object that implements an #each method, such as an Array. In this case, the array will be converted to a ‘key=key` hash before storing it.

Examples:

cabinet = HashCabinet.new 'filename'
cabinet.replace key1: 'value1', key2: 'value2'

Parameters:

  • data (Object) —

    the data to store



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# File 'lib/hash_cabinet.rb', line 173

def replace(data)
  if !data.respond_to? :each_pair and data.respond_to? :each
    data = array_to_hash data
  end

  data = normalize_types data
  transaction { |db| db.replace data }
end

#select(&block) ⇒ Hash

Returns a new Hash of key-value pairs for which the block returns true.

Returns:

  • (Hash) —

    a new Hash of key-value pairs for which the block returns true.



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# File 'lib/hash_cabinet.rb', line 183

def select(&block)
  transaction do |db|
    db.select do |key, value|
      yield key, value.from_yaml
    end.to_h.transform_values &:from_yaml
  end
end

#shift ⇒ Array

Removes a key-value pair from the database and returns them as an Array.

If the database is empty, returns nil.

Returns:

  • (Array) —

    the key and value.



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# File 'lib/hash_cabinet.rb', line 196

def shift
  transaction do |db| 
    result = db.shift
    [result[0], result[1].from_yaml]
  end
end

#to_a ⇒ Array

Returns a new array containing each key-value pair in the database.

Returns:

  • (Array) —

    a new array containing each key-value pair in the database.



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# File 'lib/hash_cabinet.rb', line 205

def to_a
  transaction do |db| 
    db.to_a.map { |pair| [pair[0], pair[1].from_yaml] }
  end
end

#to_h ⇒ hash

Returns a new hash containing each key-value pair in the database.

Returns:

  • (hash) —

    a new hash containing each key-value pair in the database.



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# File 'lib/hash_cabinet.rb', line 212

def to_h
  transaction do |db| 
    db.to_h.transform_values &:from_yaml
  end
end

#transaction {|db| ... } ⇒ Object

Note:

Under most circumstances, this method should not be used directly, as it is used by all other methods.

Yields the SDBM object to the block.

Examples:

cabinet = HashCabinet.new 'filename'

cabinet.transaction do |db|
  db.clear
end

Yield Parameters:

  • db (SDBM) —

    the SDBM instance



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# File 'lib/hash_cabinet.rb', line 48

def transaction(&block)
  SDBM.open path, &block
end

#update(data) ⇒ Object

Inserts or updates key-value pairs.

This method will work with any object which implements an #each_pair method, such as a Hash, or with any object that implements an #each method, such as an Array. In this case, the array will be converted to a ‘key=key` hash before storing it.

Examples:

cabinet = HashCabinet.new 'filename'
cabinet.update key1: 'value1', key2: 'value2'

Parameters:

  • data (Object) —

    the data to store



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# File 'lib/hash_cabinet.rb', line 230

def update(data)
  if !data.respond_to? :each_pair and data.respond_to? :each
    data = array_to_hash data
  end

  data = normalize_types data
  transaction { |db| db.update data }
end

#value?(value) ⇒ Boolean

Returns true if the database contains the given value.

Returns:

  • (Boolean) —

    true if the database contains the given value.



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# File 'lib/hash_cabinet.rb', line 240

def value?(value)
  transaction { |db| db.value? value.to_yaml }
end

#values ⇒ Array

Returns a new array containing the values in the database.

Returns:

  • (Array) —

    a new array containing the values in the database.



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# File 'lib/hash_cabinet.rb', line 245

def values
  transaction do |db| 
    db.values.map &:from_yaml
  end
end

#values_at(*key) ⇒ Array

Returns an Array of values corresponding to the given keys.

Returns:

  • (Array) —

    an Array of values corresponding to the given keys.



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# File 'lib/hash_cabinet.rb', line 252

def values_at(*key)
  transaction do |db| 
    db.values_at(*(key.map &:to_s)).map &:from_yaml
  end
end