module MultiJson::AdapterSelector

Handles adapter discovery, loading, and selection

Adapters can be specified as:

Symbol/String: adapter name (e.g., :oj, “json_gem”)
Module: adapter class directly
nil/false: use default adapter

@api private

Constants

ALIASES: Alternate spellings for adapter names
LOADERS: Strategy lambdas for loading adapters based on specification type

Public Instance Methods

default_adapter() click to toggle source

Returns the default adapter to use

@api private @return [Symbol] adapter name @example

AdapterSelector.default_adapter  #=> :oj

# File lib/multi_json/adapter_selector.rb, line 31
def default_adapter
  @default_adapter ||= detect_best_adapter
end

Private Instance Methods

detect_best_adapter() click to toggle source

Detects the best available JSON adapter

@api private @return [Symbol] adapter name

# File lib/multi_json/adapter_selector.rb, line 41
def detect_best_adapter
  loaded_adapter || installable_adapter || fallback_adapter
end

fallback_adapter() click to toggle source

Returns the fallback adapter when no others available

@api private @return [Symbol] the ok_json adapter name

# File lib/multi_json/adapter_selector.rb, line 86
def fallback_adapter
  warn_about_fallback unless @default_adapter_warning_shown
  @default_adapter_warning_shown = true
  :ok_json
end

find_loader_for(adapter_spec) click to toggle source

Finds the appropriate loader for an adapter specification

@api private @param adapter_spec [Object] adapter specification @return [Proc, nil] loader proc if found

# File lib/multi_json/adapter_selector.rb, line 122
def find_loader_for(adapter_spec)
  klass = adapter_spec.class
  return LOADERS.fetch(klass) if LOADERS.key?(klass)

  LOADERS.fetch(Module) if adapter_spec.is_a?(Module)
end

installable_adapter() click to toggle source

Tries to require and use an installable adapter

@api private @return [Symbol, nil] adapter name if successfully required

# File lib/multi_json/adapter_selector.rb, line 63
def installable_adapter
  ::MultiJson::REQUIREMENT_MAP.each_key do |adapter_name|
    return adapter_name if try_require(adapter_name)
  end
  nil
end

load_adapter(adapter_spec) click to toggle source

Loads an adapter from a specification

@api private @param adapter_spec [Symbol, String, Module, nil] adapter specification @return [Class] the adapter class

# File lib/multi_json/adapter_selector.rb, line 108
def load_adapter(adapter_spec)
  loader = find_loader_for(adapter_spec)
  return loader.call(adapter_spec, self) if loader

  raise ::LoadError, adapter_spec
rescue ::LoadError => e
  raise AdapterError.build(e)
end

load_adapter_by_name(name) click to toggle source

Loads an adapter by its string name

@api private @param name [String] adapter name @return [Class] the adapter class

# File lib/multi_json/adapter_selector.rb, line 134
def load_adapter_by_name(name)
  normalized = ALIASES.fetch(name, name).downcase
  require_relative "adapters/#{normalized}"

  class_name = normalized.split("_").map(&:capitalize).join
  ::MultiJson::Adapters.const_get(class_name)
end

loaded_adapter() click to toggle source

Finds an already-loaded JSON library

@api private @return [Symbol, nil] adapter name if found

# File lib/multi_json/adapter_selector.rb, line 49
def loaded_adapter
  return :fast_jsonparser if defined?(::FastJsonparser)
  return :oj if defined?(::Oj)
  return :yajl if defined?(::Yajl)
  return :jr_jackson if defined?(::JrJackson)
  return :json_gem if defined?(::JSON::Ext::Parser)

  :gson if defined?(::Gson)
end

try_require(adapter_name) click to toggle source

Attempts to require a JSON library

@api private @param adapter_name [Symbol] adapter to require @return [Boolean] true if require succeeded

# File lib/multi_json/adapter_selector.rb, line 75
def try_require(adapter_name)
  require ::MultiJson::REQUIREMENT_MAP.fetch(adapter_name)
  true
rescue ::LoadError
  false
end

warn_about_fallback() click to toggle source

Warns the user about using the slow fallback adapter

@api private @return [void]

# File lib/multi_json/adapter_selector.rb, line 96
def warn_about_fallback
  Kernel.warn(
    "[WARNING] MultiJson is using the default adapter (ok_json). " \
    "We recommend loading a different JSON library to improve performance."
  )
end