Class: Plumber::Context

Inherits:
Object
  • Object
show all
Defined in:
lib/plumber/context.rb

Constant Summary collapse

MAX_ASSOCIATION_COUNT = 
50

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(scope, parent = nil) ⇒ Context

Returns a new instance of Context.



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# File 'lib/plumber/context.rb', line 7

def initialize(scope, parent = nil)
  @scope = scope
  @parent = parent
  @conditions = {}
  @mapping = {}
  @associations = []
end

Instance Attribute Details

#associations ⇒ Object (readonly)

Returns the value of attribute associations.



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# File 'lib/plumber/context.rb', line 5

def associations
  @associations
end

#conditions(hash) ⇒ Object (readonly)

Returns the value of attribute conditions.



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# File 'lib/plumber/context.rb', line 5

def conditions
  @conditions
end

#mapping(hash) ⇒ Object (readonly)

Returns the value of attribute mapping.



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# File 'lib/plumber/context.rb', line 5

def mapping
  @mapping
end

#scope ⇒ Object (readonly)

Returns the value of attribute scope.



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# File 'lib/plumber/context.rb', line 5

def scope
  @scope
end

Instance Method Details

#association(name) {|context| ... } ⇒ Object

Yields:

  • (context) 


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# File 'lib/plumber/context.rb', line 23

def association(name)
  scope = record.send(name)
  context = self.class.new(scope, self)

  yield context

  @associations << context

  # Return the record defined in the yielded context:
  context.record
end

#record ⇒ Object 



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# File 'lib/plumber/context.rb', line 35

def record
  if @record.nil?
    @record = if @parent.nil?
                # If this is a top-level context, use a database query to look up an
                # existing record that matches the conditions supplied.
                @scope.where(@conditions).first
              else
                # Because ActiveRecord (currently) doesn't have an "Identity Map" feature,
                # unfortunately for associated records we can't run a DB query to find
                # existing records.
                #
                # Instead we load all records in the scope and search for one matching
                # the conditions supplied. This is why we check the scope size and raise
                # an exception if it's too large - for situations where there are
                # potentially large numbers of associated records, a separate Importer
                # instance should be defined for handling those records.
                if @scope.count > MAX_ASSOCIATION_COUNT
                  message = "%s scope contains too many records (%s)" % [
                      @scope.new.class, @scope.count
                  ]

                  raise RuntimeError, message
                end

                @scope.detect do |record|
                  @conditions.all? { |k, v| record.send(k) == v }
                end
              end

    # If an existing record hasn't been found in the scope, build a new one:
    @record ||= @scope.build

    @conditions.merge(@mapping).each do |key, value|
      @record.send("#{key}=", value)
    end
  end

  @record
end