Undefined symbol: _OBJC_CLASS_$_FlutterMethodChannel

flutter ios上会报这个错误

solution is here https://github.com/flutter/flutter/issues/17749

pod文件里加

if config.name == "Debug" || config.name == "Debug-alpha" || config.name == "Debug-live" || 
config.name == "Debug-development"
        config.build_settings['ONLY_ACTIVE_ARCH'] = 'YES'
      else
        config.build_settings['ONLY_ACTIVE_ARCH'] = 'NO'