Class: Cacheable::CacheAdapters::PersistentJsonAdapter

Inherits:
MemoryAdapter
  • Object
show all
Defined in:
lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb

Overview

Adapter that adds JSON serialization functionality to save and load in files. Also adds contexts linked to keys being fetched to support more complex cache-invalidation schemes. This works only if:

  • The cached values are JSON serializable.

  • The cache keys are strings.

  • The context information is JSON serializable.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#context ⇒ Object (readonly)

Returns the value of attribute context.



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# File 'lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb', line 16

def context
  @context
end

Instance Method Details

#clear ⇒ Object

Clear the cache



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# File 'lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb', line 60

def clear
  @context = {}
  super
end

#fetch(key, options = {}) ⇒ Object

Fetch a key with the givien cache options

Parameters

  • key (String): Key to be fetched

  • options (Hash): Cache options. The following options are interpreted by this fetch:

    • invalidate_if (Proc or nil): Optional code called to know if the cache should be invalidated for a given key:

      • Parameters

        • key (String): The key for which we check the cache invalidation

        • options (Hash): Cache options linked to this key

        • key_context (Hash): Context linked to this key, that can be set using the update_context_after_fetch callback.

      • Result

        • Boolean: Should we invalidate the cached value of this key?

    • update_context_after_fetch (Proc or nil): Optional code called when the value has been fetched for real (without cache), used to update the context

      • Parameters

        • key (String): The key for which we just fetched the value

        • value (Object): The value that has just been fetched

        • options (Hash): Cache options linked to this key

        • key_context (Hash): Context linked to this key, that is supposed to be updated in place by this callback

    • on_cache_update (Proc or nil): Optional code called once the cache has been updated

      • Parameters

        • adapter (Object): Adapter that has the cache being updated

        • key (String): The key for which we just fetched the value

        • value (Object): The value that has just been fetched

        • options (Hash): Cache options linked to this key

        • key_context (Hash): Context linked to this key

  • CodeBlock: Code called to fetch the value if not in the cache

Result

  • Object: The value for this key



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# File 'lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb', line 46

def fetch(key, options = {})
  context[key] = {} unless context.key?(key)
  key_context = context[key]
  delete(key) if options[:invalidate_if]&.call(key, options, key_context)
  return read(key) if exist?(key)

  value = yield
  options[:update_context_after_fetch]&.call(key, value, options, key_context)
  write(key, value)
  options[:on_cache_update]&.call(self, key, value, options, key_context)
  value
end

#load(file) ⇒ Object

Load the cache and context from a JSON file

Parameters

  • file (String): The file to load from



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# File 'lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb', line 86

def load(file)
  loaded_content = JSON.parse(File.read(file))
  @cache = loaded_content['cache']
  @context = loaded_content['context']
end

#save(file) ⇒ Object

Save the cache and context into a JSON file

Parameters

  • file (String): The file to save to



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# File 'lib/nexus_mods/core_extensions/cacheable/cache_adapters/persistent_json_adapter.rb', line 69

def save(file)
  # Remove from the context the keys that are not in the cache
  File.write(
    file,
    JSON.dump(
      {
        'cache' => cache,
        'context' => context.select { |key, _value| @cache.key?(key) }
      }
    )
  )
end