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