conditioner for ActiveRecord-friendly conditions from a collection

moneypenny () — Thu, 31 Aug 2006 22:02:52 GMT

I frequently have a collection of values that I want to match in an ActiveRecord query, but it would be nice if I could let ActiveRecord handle checking the data and escaping it properly. So, I wrote this method to return ActiveRecord-friendly conditions, such as: ["user_id=? AND job_id=?", 3, 4] based on the 'raw' conditions you feed to it, such as: [['user_id', 3], ['job_id', 4]]

# Returns ActiveRecord-friendly conditions based on the given

# raw conditions; handles grouping based on like field names;

# allows different boolean operators in raw conditions;

# allows different comparison operators in raw conditions;

# raw conditions setup:

# [[field name, desired value, bool. op., comp. op.], ...]

# name = condition[0]

# value = condition[1]

# bool_type = condition[2]

# comparison = condition[3]

# raw conditions example:

# [['type_id', '4', 'OR'], ['created_on', Date.new, 'AND', '<=']]

def conditioner( raw_conditions )

  return nil if raw_conditions.nil? || raw_conditions.empty?

  

  conditions = ['(']

  count = 0

  prev_name = raw_conditions[0][0]

  raw_conditions.each do |condition|

    name = condition[0]

      

    conditions[0] << ') AND ' if prev_name != name

    conditions[0] << ' ' << ( condition[2] || 'OR' ) << ' ' unless count == 0 || prev_name != name

    conditions[0] << '(' if prev_name != name

    conditions[0] << name + ' ' << ( condition[3] || '=' ) + ' ?'

      

    conditions << condition[1]

      

    prev_name = name

    count += 1

  end

  conditions[0] << ')'



  conditions

end

This way, you can do something like the following:

model_ids = Model.find( :all ).map( &:id )

raw_conditions = model_ids.collect { |id| ['model_id', id] }

conditions = conditioner( raw_conditions )

desired_collection = OtherModel.find( :all, :conditions => conditions )

If your query needs to depend on more than one factor, you might do something like the following:

if test

  raw_conditions = [['user_id', 3]]

else

  raw_conditions = [['user_id', 4], ['groups.name', 'dev']]

end



team_ids.each { |id| raw_conditions << ['team_id', id, 'AND'] }

DZone Snippets: conditions code

conditioner for ActiveRecord-friendly conditions from a collection