ble.rb

framework 'IOBluetooth'

class A
  def initialize
    @c = CBCentralManager.alloc.initWithDelegate(self, queue:nil)
  end

  def centralManagerDidUpdateState(central)
    if central.state == CBCentralManagerStatePoweredOn
      @c.scanForPeripheralsWithServices(nil, options:nil)
    end
  end

  def centralManager(central, didDiscoverPeripheral:peripheral, advertisementData:data, RSSI:rssi)
    puts NSString.stringWithFormat("peripheral: %@\nadvertisementData: %@\nrssi: %@", peripheral, data, rssi)
  end
end

A.new

NSRunLoop.currentRunLoop.run