Class: SQLExporter::Exporter_generic

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

Overview

The exporter class of a ‘generic’ sql dialect. This should be the parent for

all dialect-specific exporter classes.

Direct Known Subclasses

Exporter_mysql

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tidy) ⇒ Exporter_generic

Class constructor.



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# File 'lib/sqlexporter.rb', line 53

def initialize ( tidy )
    @tidy = tidy
    @separator = @tidy ? "\n" : " "
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args) ⇒ Object

Construct an expression string for an object’s attribute defined in

in the METHODS constant array.



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# File 'lib/sqlexporter.rb', line 99

def method_missing ( method, *args )
    obj = args[0]
    return ''  if ! obj.is_a? SQLObject
    result = ""
    _attr = obj.send method
    if _attr.is_a? Array
        result += _attr.join @separator
    elsif _attr
        result += _attr.to_s
    end
 
    return result
end

Instance Attribute Details

#separator ⇒ Object (readonly)

Returns the value of attribute separator.



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# File 'lib/sqlexporter.rb', line 48

def separator
  @separator
end

Instance Method Details

#export(obj) ⇒ Object

exports a string with a query from object.

this method should be called from a child class with defined constant
arrays [select|delete|update|insert]_syntax. methods defined in the array 
are called in the specified order for the object obj.



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# File 'lib/sqlexporter.rb', line 64

def export ( obj )
    rules_const_name = obj.class.name.sub( /^.+?::Basic([^_]+).+/, '\1' ).upcase + "_SYNTAX"
    begin
        rules = self.class.const_get( rules_const_name.to_sym )
    rescue NameError
        raise NameError, ERR_INVALID_RULES + " '" + self.send( :dialect ) + "'"
    end
    string = ""
    rules.each do |rule|
        if rule.is_a? String
            string += rule + @separator
        elsif rule.is_a? Symbol
            res = self.send( rule, obj ).to_s
            string += res
            string += @separator  if ! res.empty?
        end
    end
    return string
end

#gen_joins(obj) ⇒ Object

Generic representation of the JOIN clause



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# File 'lib/sqlexporter.rb', line 87

def gen_joins ( obj )
    arr_joins = [ ]
    if obj.gen_joins 
        arr_joins = obj.gen_joins.map { |join|  join.to_s }
    end
    return arr_joins.join( @separator )
end