Module: CouchFoo::Calculations::ClassMethods

Defined in:
lib/couch_foo/calculations.rb

Instance Method Summary collapse

Instance Method Details

#average(attribute_name, options = {}) ⇒ Object

Calculates the average value on a given property. The value is returned as a float. See calculate for examples with options.

Person.average('age')



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# File 'lib/couch_foo/calculations.rb', line 36

def average(attribute_name, options = {})
  calculate(:avg, attribute_name, options)
end

#calculate(operation, attribute_name, options = {}) ⇒ Object

This calculates aggregate values in the given property. Methods for count, sum, average, minimum, and maximum have been added as shortcuts. Options such as :conditions, :order, :count and :distinct can be passed to customize the query.

Options:

  • :conditions: A conditions hash like { :user_name => username }. See conditions in the intro.

  • :include: Named associations that should be loaded at the same time. See eager loading under Associations.

  • :order: An element to order on, eg :order => :user_name

  • :distinct: Set this to true to remove repeating elements

Examples:

Person.calculate(:count, :all) # The same as Person.count
Person.average(:age) # Find the average of people
Person.minimum(:age, :conditions => {:last_name => 'Drake'}) # Finds the minimum age for everyone with a last name other than 'Drake'
Person.sum("2 * age")



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# File 'lib/couch_foo/calculations.rb', line 78

def calculate(operation, attribute_name, options = {})
  validate_calculation_options(operation, options)
  catch :invalid_query do
    return execute_simple_calculation(operation, attribute_name, options)
  end
  0
end

#count(options = {}) ⇒ Object

Count operates using two different approaches.

  • Count all: By not passing any parameters to count, it will return a count of all the rows for the model.

  • Count using options will find the row count matched by the options used.

The second approach, count using options, accepts an option hash as the only parameter. The options are:

  • :conditions: A conditions hash like { :user_name => username }. See conditions in the intro.

  • :include: Named associations that should be loaded at the same time. See eager loading under Associations.

  • :order: An element to order on, eg :order => :user_name

  • :distinct: Set this to true to remove repeating elements

Examples for counting all:

Person.count         # returns the total count of all people

Examples for count with options:

Person.count(:conditions => {age = 26})

Note: Person.count(:all) will not work because it will use :all as the condition. Use Person.count instead.



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# File 'lib/couch_foo/calculations.rb', line 29

def count(options = {})
  calculate(:count, nil, options)
end

#maximum(attribute_name, options = {}) ⇒ Object

Calculates the maximum value on a given property. The value is returned with the same data type of the property. See calculate for examples with options.

Person.maximum('age')



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# File 'lib/couch_foo/calculations.rb', line 50

def maximum(attribute_name, options = {})
  calculate(:max, attribute_name, options)
end

#minimum(attribute_name, options = {}) ⇒ Object

Calculates the minimum value on a given property. The value is returned with the same data type of the property. See calculate for examples with options.

Person.minimum('age')



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# File 'lib/couch_foo/calculations.rb', line 43

def minimum(attribute_name, options = {})
  calculate(:min, attribute_name, options)
end

#sum(attribute_name, options = {}) ⇒ Object

Calculates the sum of values on a given property. The value is returned with the same data type of the property. See calculate for examples with options.

Person.sum('age')



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# File 'lib/couch_foo/calculations.rb', line 57

def sum(attribute_name, options = {})
  calculate(:sum, attribute_name, options)
end