どうもお久しぶりです。

morimotoです。

今日は複雑なActiveRecordの条件句を作成する際に（もしかしたら）楽になるのではないかと思いconditionを生成するクラスを作ってみました。

  class ARCond
    module OPERATION
      EQUAL            = '='
      NOT_EQUAL        = '<>'
      IN               = 'IN'
      GREATER          = '>'
      GREATER_OR_EQUAL = '>='
      LESS             = '< '
      LESS_OR_EQUAL    = '<='
    end

    attr_reader :conditions, :parameters, :separator, :table_name

    def initialize(separator="AND", table_name=nil)
      @conditions = []
      @parameters = []
      @separator  = separator
      @table_name = table_name
    end

    # column = ?
    def equal(column, value, table=nil)
      add(column, value, OPERATION::EQUAL, table)
    end
    # column <> ?
    def not_equal(column, value, table=nil)
      add(column, value, OPERATION::NOT_EQUAL, table)
    end
    # column IN (?,?,?...)
    def in(column, value, table=nil)
      add(column, value, OPERATION::IN, table)
    end
    # column > ?
    def greater(column, value, table=nil)
      add(column, value, OPERATION::GREATER, table)
    end
    # column >= ?
    def greater_or_equal(column, value, table=nil)
      add(column, value, OPERATION::GREATER_OR_EQUAL, table)
    end
    # column < ?
    def less(column, value, table=nil)
      add(column, value, OPERATION::LESS, table)
    end
    # column <= ?
    def less_or_equal(column, value, table=nil)
      add(column, value, OPERATION::LESS_OR_EQUAL, table)
    end

    def << (other)
      cond = nil
      param = []
      if other.kind_of? ARCond
        c = other.build
        cond = c.delete_at(0)
        param = c
      elsif other.kind_of? String
        cond = other
      elsif other.kind_of? Array
        cond = other.delete_at(0)
        param = other
      end
      unless cond.blank?
        @conditions << cond
        @parameters.concat(param)
      end
      return self.build
    end

    # [conditions, param, param, param,...]
    def build
      [join_conditions].concat(@parameters)
    end

    private
    def join_conditions
      sep = " #{@separator} "
      "(#{@conditions.join(sep)})"
    end

    def column_fullname(column, table=nil)
      unless column =~ /^[\w]+\.[\w]+$/
        if table_name = table.blank? ? @table_name : table
          return "#{table_name}.#{column}"
        end
      end
      column
    end

    def add(column, value, operation, table=nil)
      parts = [column_fullname(column, table), operation]
      param = [value].flatten
      parts <<1", true, nil, 31, 32, 33]



# 連結文字を変更する
c2 = ARCond.new("OR")

# 指定した連結文字で結合されていく
c2.greater("col4", 100)
  # => ["(col4 > ?)", 100]
c2.less("col4", 200)
  # => ["(col4 > ? OR col4 < ?)", 100, 200]

# 配列みたいに追加していく
c1 << c2
  # => ["(col1 = ? AND col2 <> ? AND col3 IN (?,?,?) AND (col4 > ? OR col4 < ?))", true, nil, 31, 32, 33, 100, 200]



# 引数なしはANDで連結
c3 = ARCond.new()

# いつもどおりの配列の conditions もくっつけれる
c3 << ["col5 = ? AND col6 IN (?,?)", 11,22,33]
  # => ["(col5 = ? AND col6 IN (?,?))", 11, 22, 33]

# 任意文字列もくっつけれる
c3 < < "col7 > col8"
  # => ["(col5 = ? AND col6 IN (?,?) AND col7 > col8)", 11, 22, 33]


# テーブル名を指定する
c4 = ARCond.new("OR", "sample")

# カラム名の頭にテーブル名が付与される
c4.greater_or_equal("col9", 300)
  # => ["(sample.col9 >= ?)", 300]
c4.less_or_equal("col9", 400)
  # => ["(sample.col9 >= ? OR sample.col9 < = ?)", 300, 400]

# くっつけるときにテーブル名を指定する
c4.equal("col10", false, "banana")
  # => ["(sample.col9 >= ? OR sample.col9 < = ? OR banana.col10 = ?)", 300, 400, false]

c3 << c4
  # => ["(col5 = ? AND col6 IN (?,?) AND col7 > col8 AND (sample.col9 >= ? OR sample.col9 < = ? OR banana.col10 = ?))", 11, 22, 33, 300, 400, false]

c1 << c3
  # => ["(col1 = ? AND col2 <> ? AND col3 IN (?,?,?) AND (col4 > ? OR col4 < ?) AND (col5 = ? AND col6 IN (?,?) AND col7 > col8 AND (sample.col9 >= ? OR sample.col9 < = ? OR banana.col10 = ?)))", true, nil, 31, 32, 33, 100, 200, 11, 22, 33, 300, 400, false]


# 最終的に使いたいタイミングで build してあげたらよい
c1.build
  # => ["(col1 = ? AND col2 <> ? AND col3 IN (?,?,?) AND (col4 > ? OR col4 < ?) AND (col5 = ? AND col6 IN (?,?) AND col7 > col8 AND (sample.col9 >= ? OR sample.col9 < = ? OR banana.col10 = ?)))", true, nil, 31, 32, 33, 100, 200, 11, 22, 33, 300, 400, false]

1. operation == OPERATION::IN) ? "(#{param.map{'?'}.join(',')})" : "?") self < < [parts.join(' ')].concat(param) end end

   使い方の例）

   # 基本スタイル
   c1 = ARCond.new("AND")
   c1.equal("col1", true)
     # => ["(col1 = ?)", true]
   c1.not_equal("col2", nil)
     # => ["(col1 = ? AND col2 <> ?)", true, nil]
   c1.in("col3", [31,32,33])
     # => ["(col1 = ? AND col2 <> ? AND col3 IN (?,?,? [↩]