Class: CaRuby::Cache

Inherits:
Object
  • Object
show all
Defined in:
lib/caruby/database/cache.rb

Overview

Cache for objects held in memory and accessed by key.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize {|obj| ... } ⇒ Cache

Returns a new instance of Cache.

Yields:

  • (obj) —

    returns the key for the given object to cache

Yield Parameters:

  • obj —

    the object to cache



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# File 'lib/caruby/database/cache.rb', line 12

def initialize
  # Make the class => {object => {key => object}} hash.
  # The {object => {key => object}} hash is an Associative which converts the given
  # object to its key by calling the block given to this initializer.
  # The {{key => object} hash takes a key as an argument and returns the cached object.
  # If there is no cached object, then the object passed to the Associative is cached. 
  @ckh = Jinx::LazyHash.new do
    kh = Hash.new 
    # the obj => key associator
    assoc = Jinx::Associative.new do |obj|
      key = yield(obj)
      kh[key] if key
    end
    # the obj => key => value writer  
    assoc.writer do |obj, value|
      key = yield(obj)                                                                       
      raise ArgumentError.new("caRuby cannot cache object without a key: #{obj}") if key.nil?
      kh[key] = value
    end
  end
  @sticky = Set.new
end

Instance Attribute Details

#sticky ⇒ Object (readonly)

The classes which are not cleared when #clear is called.



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# File 'lib/caruby/database/cache.rb', line 8

def sticky
  @sticky
end

Instance Method Details

#[](item) ⇒ Object

If there is already a cached object with the same key as the given item, then this method returns that cached object. Otherwise, this method caches the given item and returns that item.

Parameters:

  • item —

    the object to resolve

Returns:

  • the object cached with the same class and key as the given item

Raises:

  • (ArgumentError) —

    if the item does not have a key



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# File 'lib/caruby/database/cache.rb', line 42

def [](item)
  @ckh[item.class][item]
end

#add(item) ⇒ Object

Adds the given item to this cache, unless one already exists.

Parameters:

  • item —

    the object to cache

Returns:

  • the cached item



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# File 'lib/caruby/database/cache.rb', line 50

def add(item)
  @ckh[item.class][item] ||= item
end

#add!(item) ⇒ Object

Adds the given item to this cache. Overwrites an existing cache entry for the given item’s key, if one already exists.

Parameters:

  • item —

    the object to cache



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# File 'lib/caruby/database/cache.rb', line 58

def add!(item)
  @ckh[item.class][item] = item
end

#clear ⇒ Object

Clears the non-sticky class caches.



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# File 'lib/caruby/database/cache.rb', line 63

def clear
  if @sticky.empty? then
    @ckh.clear
  else
    @ckh.each { |klass, ch| ch.clear unless @sticky.include?(klass) }
  end
end