The sandbox is not in sync with

在Flutter项目中，运行iOS设备运行项目的时候，报错如下所示：

The sandbox is not in sync with the Podfile.lock. Run 'pod install' or update your CocoaPods install

执行：

pod install

依然报错：

Could not find 'ffi' (>= x.x.0) among xxx total gem(s) (Gem::MissingSpecError)

网上找的方法均无解，最后，执行

sudo gem install cocoapods

ok!
参考官网：https://guides.cocoapods.org/using/getting-started.html#installation