Xcode 10 报Error: Multiple commands produce类型的错误处理
每次升级Xcode后运行项目都会藏有彩蛋
报错：
Error: Multiple commands produce
Multiple commands produce '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/README.md':
1) Target 'NoCarCarriers' (project 'NoCarCarriers') has copy command from '/Users/zgw/Desktop/trunk_LRS/NoCarCarriers/NoCarCarriers/Tools/MJRefresh/README.md' to '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/README.md'
Multiple commands produce '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/Info.plist':
1) Target 'NoCarCarriers' (project 'NoCarCarriers') has copy command from '/Users/zgw/Desktop/trunk_LRS/NoCarCarriers/NoCarCarriers/Tools/Masonry/Info.plist' to '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/Info.plist'
Xcode10使用了一个的新创建系统，比之前的提供更好的可靠性与创建性能，而且可以获取项目配置问题（默认设置新创建系统）
Build System
Again, Xcode 10 uses a new build system. The new build system provides improved reliability and build performance, and it catches project configuration problems that the legacy build system does not.
The legacy build system is still available in Xcode 10. To use the legacy build system, select it in the File > Project/Workspace Settings sheet. Projects configured to use the legacy build system will display an orange hammer icon in the Activity View.
在苹果文档中，提及Xcode10中的关于旧项目New Build System更改适配中提及到以下两点
The new build system has stricter checks for cycles between elements in the build in order to prevent unnecessary rebuilds.
It is an error for any individual file in the build to be produced by more than one build command. For example, if two targets each declare the same output file from a shell script phase, factor out the declaration of the output file into a single target.
New Build System会对构建中的元素循环进行严格的检查，避免不必要的重建，这个就是错误出现的原因。
错误发生的普遍形式：
1.info.plist
Multiple commands produce '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/Info.plist':
2.README.md
Multiple commands produce '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/README.md':
3.LICENSE
Multiple commands produce '/Users/zgw/Library/Developer/Xcode/DerivedData/NoCarCarriers-awieesrvtoxgprhdtiipzcduxlho/Build/Products/Debug-iphonesimulator/NoCarCarriers.app/LICENSE':
4.Copy Pods Resources
有两种解决方法:
一、不使用New Build System
在File > Project/Workspace Settings中的Share Project/Workspace Settings 里build system 将 New Build System(Default) 切换成Legacy build system。
图一
二、根据出错信息，在新创建系统模式下，去掉多余的引用。
图二
关于Copy Pods Resources每次pod install之后都会出现问题的解决方案，更新cocoaPod到最新版本
终端：gem install cocoapods --pre
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