Class: PluckMap::Attribute

Inherits:
Object
  • Object
show all
Defined in:
lib/pluck_map/attribute.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(id, options = {}) ⇒ Attribute 



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# File 'lib/pluck_map/attribute.rb', line 5

def initialize(id, options={})
  @id = id
  @selects = Array(options.fetch(:select, id))
  @name = options.fetch(:as, id)
  @alias = name.to_s.tr("_", " ")
  @block = options[:map]

  if options.key? :value
    @value = options[:value]
    @selects = []
  else
    raise ArgumentError, "You must select at least one column" if selects.empty?
    raise ArgumentError, "You must define a block if you are going to select " <<
      "more than one expression from the database" if selects.length > 1 && !block
  end
end

Instance Attribute Details

#alias ⇒ Object (readonly)

Returns the value of attribute alias.



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# File 'lib/pluck_map/attribute.rb', line 3

def alias
  @alias
end

#block ⇒ Object (readonly)

Returns the value of attribute block.



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# File 'lib/pluck_map/attribute.rb', line 3

def block
  @block
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



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# File 'lib/pluck_map/attribute.rb', line 3

def id
  @id
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/pluck_map/attribute.rb', line 3

def name
  @name
end

#selects ⇒ Object (readonly)

Returns the value of attribute selects.



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# File 'lib/pluck_map/attribute.rb', line 3

def selects
  @selects
end

Instance Method Details

#apply(object) ⇒ Object 



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# File 'lib/pluck_map/attribute.rb', line 22

def apply(object)
  block.call(*object)
end

#keys ⇒ Object

These are the names of the values that are returned from the database (every row returned by the database will be a hash of key-value pairs)

If we are only selecting one thing from the database then the PluckMapPresenter will automatically alias the select-expression, so the key will be the alias.



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# File 'lib/pluck_map/attribute.rb', line 33

def keys
  selects.length == 1 ? [self.alias] : selects
end

#no_map? ⇒ Boolean 



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# File 'lib/pluck_map/attribute.rb', line 37

def no_map?
  block.nil?
end

#to_ruby(keys) ⇒ Object

When the PluckMapPresenter performs the query, it will receive an array of rows. Each row will itself be an array of values.

This method constructs a Ruby expression that will extract the appropriate values from each row that correspond to this Attribute.

The array of values will be correspond to the array of keys. This method determines which values pertain to it by figuring out which order its keys were selected in



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# File 'lib/pluck_map/attribute.rb', line 52

def to_ruby(keys)
  return @value.inspect if defined?(@value)
  indexes = self.keys.map { |key| keys.index(key) }
  return "values[#{indexes[0]}]" if indexes.length == 1 && !block
  ruby = "values.values_at(#{indexes.join(", ")})"
  ruby = "invoke(:\"#{id}\", #{ruby})" if block
  ruby
end