error: 'Flutter/Flutter.h' file not found when flutter run on iOS

I found a solution!

1. Backup ios/Runner folder.

2. Delete the ios folder.

3. Run flutter create (your project name). in the previous folder where you have your project(cd users/user/"projects_folder") (this will recreate your ios folder).

4. Paste your Runner backup in the ios folder (into the project).

5. Open Runner.xcworkspace (into ios folder) and there, check the Version, the Bundle ID, all the info.

6. (If do you Have Firebase, you have to copy and paste again the Google Service-Info.Plist into the Runner folder (Always through Xcode) (If do you do this manually, it doesn't work).

Finally, flutter run and should work!

If flutter run fails:

1. cd ios
2. pod install
3. cd ..
4. flutter run

This solution worked for me:

Changing PodFile from:

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
    config.build_settings['ENABLE_BITCODE'] = 'NO'
    config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '10.0'
    end
  end
end

to

post_install do |installer|
  installer.pods_project.targets.each do |target| 
    flutter_additional_ios_build_settings(target)
  end
end

A way easier solution:

1. Remove ios/Flutter/Flutter.podspec: rm ios/Flutter/Flutter.podspec
2. flutter clean
3. Run your app again.

Taken from here