Module: Factree::FactSource

Defined in:
lib/factree/fact_source.rb

Overview

Mixin to help define fact source classes.

Defined Under Namespace

Modules: ClassMethods

Constant Summary collapse

UndefinedFactError = 
Class.new(StandardError)
UnknownFactError = 
Class.new(StandardError)
UNKNOWN_FACT = 
"Attempted to determine the value of a fact that is unknown".freeze

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(base) ⇒ Object 



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# File 'lib/factree/fact_source.rb', line 7

def self.included(base)
  base.extend(ClassMethods)
end

.to_combined_h(*sources) ⇒ Object

Takes several FactSources and returns a single hash containing all of their facts mixed together.



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# File 'lib/factree/fact_source.rb', line 94

def self.to_combined_h(*sources)
  sources.map(&:to_h).inject({}, &:merge)
end

Instance Method Details

#[](fact_name) ⇒ Object

Returns the value of the fact, or nil if the value is unknown



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# File 'lib/factree/fact_source.rb', line 48

def [](fact_name)
  fetch(fact_name) { nil }
end

#ensure_defined(fact_name) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/factree/fact_source.rb', line 70

def ensure_defined(fact_name)
  unless self.class.defined? fact_name
    raise UndefinedFactError, "undefined fact referenced: #{fact_name}"
  end
end

#fetch(fact_name, &block) ⇒ Object

Returns the value of the fact.

If the value is unknown, then the block will be called with the name of the fact. If no block is supplied, then an UnknownFactError will be raised.



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# File 'lib/factree/fact_source.rb', line 55

def fetch(fact_name, &block)
  ensure_defined fact_name
  fact_proc = self.class.fact_procs[fact_name]

  fact_value = nil
  fact_known = catch(UNKNOWN_FACT) do
    fact_value = instance_eval(&fact_proc)
    true
  end
  return fact_value if fact_known

  fetch_unknown(fact_name, &block)
end

#fetch_unknown(fact_name) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Raises:



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# File 'lib/factree/fact_source.rb', line 77

def fetch_unknown(fact_name)
  return yield(fact_name) if block_given?

  raise UnknownFactError, "unknown fact: #{fact_name}"
end

#known?(fact_name) ⇒ Boolean

Checks to see if the value of the fact is known.

Returns:

  • (Boolean) 


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# File 'lib/factree/fact_source.rb', line 42

def known?(fact_name)
  fetch(fact_name) { return false }
  true
end

#to_h ⇒ Object

A hash mapping all of the known fact names to values.



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# File 'lib/factree/fact_source.rb', line 84

def to_h
  self.class.fact_procs.flat_map { |fact_name, _fact_proc|
    fact_known = true
    fact_value = fetch(fact_name) { fact_known = false }

    fact_known ? [[fact_name, fact_value]] : []
  }.to_h
end

#unknown ⇒ Object

Calling this method in a fact proc will signal that the fact’s value is unknown.



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# File 'lib/factree/fact_source.rb', line 99

def unknown
  throw UNKNOWN_FACT
end