Using feature flag as kill switch in different version of mobile application

Question

I want to use feature flags as a kill switch if something goes wrong in my mobile app release. To quickly get the features on the app to the last working version of the feature or to completely hide the feature. But I have a logical doubt related to how can manage the same feature flag in the following version of the application after that I killed the feature in a previous version of the app. 
Example scenario 
On day 1 I develop a new feature A. I implement feature toggle A on this new feature and then  deploy it on play store myApp 1.0 with feature toggle A turned ON (server-side)
On day 2 I noticed that something went wrong on feature A so I kill switch it turning OFF feature toggle A (server-side) then  I fixed the  "client-side" feature A. I deploy on play store myApp 1.1 with the fixed version of the feature
But now I can't turn ON (server-side) feature toggle A again because it would open the feature on the bot version of the app.
 I want to implement a new toggle every time that I use the kill switch? Any suggestion or link?

Answer 1

As per the Feature Flag perspective, you can use the version of the application as part of the logic to turn on or off the flag for the specific user.
Don’t think of feature flags as just on or off for all users, but as a way to turn a feature on or off for a specific user or set of users. For example, in DevCycle Mobile SDK you can set up the Feature Flag to be on for a specific version but off for the other.

let user = try DVCUser.builder()
.appBuild(1005)
.appVersion("1.1")
.build()

client.identifyUser(user)

Then you can use a boolean feature flag to show or hide the new component based upon the version of the app they are using.

let newFeature: DVCVariable<Bool> = client.variable(key: "new-feature", defaultValue: false)
You can also control which API the user accesses based upon their appVersion.
let apiVersion: DVCVariable<String> = client.variable(key: "api-version", defaultValue: "1.0")
 

For this Feature Flag, the default value of the API is set to “1.0”. In the UI you can then set the Feature Flag to return “1.1” if the appVersion is set to 1.1.

Hope this helps.