Class: ActiveRecord::Base

Inherits:
Object show all
Defined in:
lib/api_hammer/active_record_cache_find_by.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.cache_find_by(*attribute_names) ⇒ Object

causes requests to retrieve a record by the given attributes (all of them) to be cached. this is for single records only. it is unsafe to use with a set of attributes whose values (in conjunction) may be associated with multiple records.

see .finder_cache and .find_cache= for where it is cached.

flush_find_cache is defined on the instance. it is called on save to clear an updated record from

the cache. it may also be called explicitly to clear a record from the cache.

beware of multiple application servers with different caches - a record cached in multiple will not be invalidated in all when it is saved in one.



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# File 'lib/api_hammer/active_record_cache_find_by.rb', line 87

def cache_find_by(*attribute_names)
  unless cache_find_bys
    # initial setup
    self.cache_find_bys = Set.new
    after_update :flush_find_cache
    before_destroy :flush_find_cache
  end

  find_by = attribute_names.map do |name|
    raise(ArgumentError) unless name.is_a?(Symbol) || name.is_a?(String)
    name.to_s.dup.freeze
  end.sort.freeze

  self.cache_find_bys = (cache_find_bys | [find_by]).freeze
end

.finder_cache ⇒ Object

the cache. should be an instance of some sort of ActiveSupport::Cache::Store. by default uses Rails.cache if that exists, or creates a ActiveSupport::Cache::MemoryStore to use. set this per-model or on ActiveRecord::Base, as needed; it is inherited.



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# File 'lib/api_hammer/active_record_cache_find_by.rb', line 69

def finder_cache
  # if this looks weird, it kind of is. on the first invocation of #finder_cache, we call finder_cache= 
  # which overwrites the finder_cache method, and this then calls the newly defined method. 
  self.finder_cache = (Object.const_defined?(:Rails) && ::Rails.cache) || ::ActiveSupport::Cache::MemoryStore.new
  self.finder_cache
end

.finder_cache=(val) ⇒ Object 



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# File 'lib/api_hammer/active_record_cache_find_by.rb', line 62

def finder_cache=(val)
  define_singleton_method(:finder_cache) { val }
end

Instance Method Details

#flush_find_cache ⇒ Object

clears this record from the cache used by cache_find_by



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# File 'lib/api_hammer/active_record_cache_find_by.rb', line 124

def flush_find_cache
  self.class.send(:cache_find_bys).each do |attribute_names|
    find_attributes = attribute_names.map { |attr_name| [attr_name, attribute_was(attr_name)] }
    self.class.instance_exec(find_attributes) do |find_attributes|
      finder_cache.delete(cache_key_for(find_attributes))
    end
  end
  nil
end