Class: SQLite3::Translator

Inherits:
Object
  • Object
show all
Defined in:
lib/sqlite3/translator.rb

Overview

The Translator class encapsulates the logic and callbacks necessary for converting string data to a value of some specified type. Every Database instance may have a Translator instance, in order to assist in type translation (Database#type_translation).

Further, applications may define their own custom type translation logic by registering translator blocks with the corresponding database's translator instance (Database#translator).

Instance Method Summary (collapse)

Constructor Details

- (Translator) initialize

Create a new Translator instance. It will be preinitialized with default translators for most SQL data types.



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# File 'lib/sqlite3/translator.rb', line 18

def initialize
  @translators = Hash.new( proc { |type,value| value } )
  @type_name_cache = {}
  register_default_translators
end

Instance Method Details

- (Object) add_translator(type, &block)

Add a new translator block, which will be invoked to process type translations to the given type. The type should be an SQL datatype, and may include parentheses (i.e., "VARCHAR(30)"). However, any parenthetical information is stripped off and discarded, so type translation decisions are made solely on the "base" type name.

The translator block itself should accept two parameters, "type" and "value". In this case, the "type" is the full type name (including parentheses), so the block itself may include logic for changing how a type is translated based on the additional data. The "value" parameter is the (string) data to convert.

The block should return the translated value.



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# File 'lib/sqlite3/translator.rb', line 37

def add_translator( type, &block ) # :yields: type, value
  warn(<<-eowarn) if $VERBOSE
#{caller[0]} is calling `add_translator`.
Built in translators are deprecated and will be removed in version 2.0.0
  eowarn
  @translators[ type_name( type ) ] = block
end

- (Object) translate(type, value)

Translate the given string value to a value of the given type. In the absense of an installed translator block for the given type, the value itself is always returned. Further, nil values are never translated, and are always passed straight through regardless of the type parameter.



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# File 'lib/sqlite3/translator.rb', line 49

def translate( type, value )
  unless value.nil?
    # FIXME: this is a hack to support Sequel
    if type && %w{ datetime timestamp }.include?(type.downcase)
      @translators[ type_name( type ) ].call( type, value.to_s )
    else
      @translators[ type_name( type ) ].call( type, value )
    end
  end
end