error Failed to build iOS project. We ran "xcodebuild" command but it exited with error code 65

If you don't have cocoa pods installed you need to sudo gem install cocoapods

1. run cd ios
2. run pod install
3. cd ..
4. delete build folder
5. run react-native run-ios

if error persists, 1. delete build folder again 2. open the /ios folder in x-code3. navigate File -> Project Settings -> Build System -> change (Shared workspace settings and Per-User workspace settings): Build System -> Legacy Build System

1. delete the build/ folder in ios/ and rerunif that doesn't do any change then
2. File -> Project Settings (or WorkSpace Settings) -> Build System -> Legacy Build System
3. Rerun and voilà!

In case this doesn't work, don't be sad, there is another solution to deeply clean project

1. Delete ios/ and android/ folders.

2. Run react-native eject

3. Run react-native link

4. react-native run-ios

This will bring a whole new resurrection for your project

SOLVED: Always be sure to update your Xcode folks!

Protip: And don't do it from the apple store (but always do it from an official apple website of course)

tip from: http://ericasadun.com/2016/03/22/xcode-upgrades-lessons-learned/

official apple download page: https://developer.apple.com/download/more/

For those who are unable to resolve with above method

1. Go to project settings in Xcode. Menu File->Project Settings

2. Go to per-User Project Settings section.

3. Click on advanced.

4. Select Xcode Default option. previously this used to be Legacy for my project.

I have analysed on similar lines and concluded that clean is causing the archive to fail. So, the new build system is not clearing the custom/legacy build directory.

delete the build/ folder in ios/ and rerun if that doesn't do any change thenFile -> Project Settings (or WorkSpace Settings) -> Build System -> Legacy Build SystemRerun and voilà!

If it still Fails you need to clean full project

Do the following:

• Delete ios dir manually
• Clean cache Run npm cache clean --force
• Run react-native eject
• Re-install all packages npm install
• Run the link command react-native link
• Finally run react-native run-ios