Class: Axiom::Evaluator::Context

Inherits:
BasicObject
Extended by:
Aliasable
Defined in:
lib/axiom/support/evaluator.rb

Overview

Provide a context to evaluate a Relation operation block

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Aliasable

inheritable_alias

Constructor Details

#initialize(header) ⇒ undefined

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.

Initialize a Context



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# File 'lib/axiom/support/evaluator.rb', line 33

def initialize(header)
  @header    = header
  @functions = ::Hash.new
  @yield     = yield self
  @functions.freeze
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name, *args) ⇒ Attribute (private)

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.

Lookup the attribute in the header using the attribute name

Examples:

attribute = context.id



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# File 'lib/axiom/support/evaluator.rb', line 117

def method_missing(name, *args)
  super unless respond_to?(name)
  ::Kernel.raise ::ArgumentError, "wrong number of arguments (#{args.length} for 0)" unless args.empty?
  self[name]
end

Instance Attribute Details

#functions ⇒ Hash (readonly)

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.

The functions to evaluate



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# File 'lib/axiom/support/evaluator.rb', line 17

def functions
  @functions
end

#yield ⇒ Object (readonly)

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.

Return the block results



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# File 'lib/axiom/support/evaluator.rb', line 24

def yield
  @yield
end

Instance Method Details

#[](name) ⇒ Attribute

Lookup the attribute in the header

Examples:

attribute = context[name]



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# File 'lib/axiom/support/evaluator.rb', line 79

def [](name)
  @header[name]
end

#add(attribute, object = Undefined) { ... } ⇒ self

Add a function to be evaluated by the summarization operation

Examples:

of a function

context.add(:total, context[:unit_price] * context[:quantity])

of a block

context.add(:total) { |tuple| tuple[:unit_price] * tuple[:quantity] } }

Yields:

  • [] optional block to execute in the summarization operation



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# File 'lib/axiom/support/evaluator.rb', line 59

def add(attribute, object = Undefined, &block)
  object = block if object.equal?(Undefined)
  type   = Attribute.infer_type(object)
  klass  = Attribute.descendants.detect do |descendant|
    descendant.type >= type
  end
  functions[klass.coerce(attribute)] = object
  self
end

#respond_to?(name) ⇒ Boolean

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.

Test if the method is supported on this object



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# File 'lib/axiom/support/evaluator.rb', line 90

def respond_to?(name, *)
  @header.any? { |attribute| attribute.name.equal?(name) }
end

#send(*args, &block) ⇒ 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.

Forward a message to the object



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# File 'lib/axiom/support/evaluator.rb', line 101

def send(*args, &block)
  __send__(*args, &block)
end