我已经使用Objective-C在Cocoa中编写了一个笔记应用程序，它会启动但是当我保存文件时它会显示：http://imgur.com/a/zXTgX。即使约束条件正常，控制台也是默认的：
2017-04-17 14:21:42.095495+0300 Notes[4650:343877] Attempting to access document's contents, but none found!
2017-04-17 14:21:42.152172+0300 Notes[4650:343877] [Layout] Detected missing constraints for <NSTextField: 0x10027aaf0>. It cannot be placed because there are not enough constraints to fully define the size and origin. Add the missing constraints, or set translatesAutoresizingMaskIntoConstraints=YES and constraints will be generated for you. If this view is laid out manually on macOS 10.12 and later, you may choose to not call [super layout] from your override. Set a breakpoint on DETECTED_MISSING_CONSTRAINTS to debug. This error will only be logged once.