Firebase 已经更新到 4.0，它破坏了很多代码，所以我需要将我的安装保持在 3.x-ish。我以前从未这样做过，所以对我来说，但我得到这样的错误：
[!] Unable to satisfy the following requirements:
- `Firebase/RemoteConfig (= 1.3.4)` required by `Podfile`
- `Firebase/RemoteConfig (= 1.3.4)` required by `Podfile`
None of your spec sources contain a spec satisfying the dependency: `Firebase/RemoteConfig (= 1.3.4)`.
You have either:
* out-of-date source repos which you can update with `pod repo update` or with `pod install --repo-update`.
* mistyped the name or version.
* not added the source repo that hosts the Podspec to your Podfile.
Note: as of CocoaPods 1.0, `pod repo update` does not happen on `pod install` by default.
这是我试图冻结在我的 podfile 中的方式：
pod 'Firebase/Database', '3.1.2'
pod 'Firebase/Auth', '3.1.1'
pod 'Firebase/RemoteConfig', '1.3.4'
pod 'Firebase/Messaging', '1.2.3'
顺便说一句，我试图pod repo update无济于事。