Class: Amalgalite::Function

Inherits:
Object
  • Object
show all
Defined in:
lib/amalgalite/function.rb

Overview

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 :

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, arity) ⇒ Function

Initialize the function with a name and arity



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# File 'lib/amalgalite/function.rb', line 42

def initialize( name, arity )
  @name = name
  @arity = arity
end

Instance Attribute Details

#arity ⇒ Object

The arity of the SQL function



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# File 'lib/amalgalite/function.rb', line 39

def arity
  @arity
end

#name ⇒ Object

The name of the SQL function



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# File 'lib/amalgalite/function.rb', line 36

def name
  @name
end

Instance Method Details

#signature ⇒ Object

Do Not Override

The function signature for use by the Amaglaite datase in tracking function definition and removal.



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# File 'lib/amalgalite/function.rb', line 57

def signature
  @signature ||= ::Amalgalite::SQLite3::Database::Function.signature( self.name, self.arity )
end

#to_proc ⇒ Object

All SQL functions defined foloow the to_proc protocol



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# File 'lib/amalgalite/function.rb', line 48

def to_proc
  self
end