Class: Candy::CandyArray

Inherits:
Object
  • Object
show all
Includes:
Crunch, Embeddable
Defined in:
lib/candy/array.rb

Overview

An array-like object that saves itself to a parent Candy::Piece object. MongoDB’s atomic array operators are used extensively to perform concurrency-friendly updates of individual array elements without rewriting the whole array.

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Embeddable

#candy_adopt

Methods included from Crunch

#findAndModify, included

Constructor Details

#initialize(*args) ⇒ CandyArray

Sets the initial array state.



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# File 'lib/candy/array.rb', line 20

def initialize(*args)
  @__candy = from_candy(args)
  super()
end

Class Method Details

.embed(parent, attribute, *args) ⇒ Object

Creates the object with parent and attribute values set properly on the object and any children.



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# File 'lib/candy/array.rb', line 14

def self.embed(parent, attribute, *args)
  this = self.new(*args)
  this.candy_adopt(parent, attribute)
end

Instance Method Details

#<<(val) ⇒ Object Also known as: push

Appends a value to our array.



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# File 'lib/candy/array.rb', line 40

def <<(val)
  property = candy_coat(@__candy_parent_key, val)
  @__candy_parent.operate :push, @__candy_parent_key => property
  self.candy << property
end

#==(val) ⇒ Object

Array equality.



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# File 'lib/candy/array.rb', line 68

def ==(val)
  self.to_ary == val
end

#[](index) ⇒ Object

Retrieves the value from our internal array.



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# File 'lib/candy/array.rb', line 35

def [](index)
  candy[index]
end

#[]=(index, val) ⇒ Object

Set a value at a specified index in our array. Note that this operation _does not_ confirm that the array in Mongo still matches our current state. If concurrent updates have happened, you might end up overwriting something other than what you thought.



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# File 'lib/candy/array.rb', line 28

def []=(index, val)
  property = candy_coat(nil, val)  # There are no attribute names on array inheritance
  @__candy_parent.set embedded(index => property)
  self.candy[index] = property
end

#candy ⇒ Object Also known as: to_candy, to_ary

Returns the array of memoized values.



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# File 'lib/candy/array.rb', line 56

def candy
  @__candy ||= []
end

#from_candy(array) ⇒ Object

Unwraps all elements of the array, telling them who their parent is. The attribute doesn’t matter because arrays don’t have them.



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# File 'lib/candy/array.rb', line 63

def from_candy(array)
  array.map {|element| Wrapper.unwrap(element, self)}
end

#length ⇒ Object Also known as: size

Array length.



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# File 'lib/candy/array.rb', line 73

def length
  self.to_ary.length
end

#shift(n = 1) ⇒ Object

Pops the front off the MongoDB array and returns it, then resyncs the array. (Thus supporting real-time concurrency for queue-like behavior.)



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# File 'lib/candy/array.rb', line 49

def shift(n=1)
  doc = @__candy_parent.collection.find_and_modify query: {"_id" => @__candy_parent.id}, update: {'$pop' => {@__candy_parent_key => -1}}, new: false
  @__candy = doc[@__candy_parent_key.to_s]
  @__candy.shift
end