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require 'amalgalite/sqlite3/database/function'
module Amalgalite
#
# A Base class to inherit from for creating your own SQL scalar functions
# in ruby.
#
# These are SQL functions similar to _abs(X)_, _length(X)_, _random()_. Items
# that take parameters and return value. They have no state between
# calls. Built in SQLite scalar functions are :
#
# * http://www.sqlite.org/lang_corefunc.html
# * http://www.sqlite.org/lang_datefunc.html
#
# Functions defined in Amalgalite databases conform to the Proc interface.
# Everything that is defined in an Amalgalite database using +define_function+
# has its +to_proc+ method called. As a result, any Function must also
# conform to the +to_proc+ protocol.
#
# If you choose to use Function as a parent class of your SQL scalar function
# implementation you should only have implement +call+ with the appropriate
# _arity_.
#
# For instance to implement a _sha1(X)_ SQL function you could implement it as
#
# class SQLSha1 < ::Amalgalite::Function
# def initialize
# super( 'md5', 1 )
# end
# def call( s )
# ::Digest::MD5.hexdigest( s.to_s )
# end
# end
#
class Function
# The name of the SQL function
attr_accessor :name
# The arity of the SQL function
attr_accessor :arity
# Initialize the function with a name and arity
def initialize( name, arity )
@name = name
@arity = arity
end
# All SQL functions defined foloow the +to_proc+ protocol
def to_proc
self
end
# <b>Do Not Override</b>
#
# The function signature for use by the Amaglaite datase in tracking
# function definition and removal.
#
def signature
@signature ||= ::Amalgalite::SQLite3::Database::Function.signature( self.name, self.arity )
end
end
end
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83 entries across 83 versions & 2 rubygems