Intercepting calls from your app even from the background

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From Apple documentation:

Use the CTCallCenter class to obtain a list of current cellular calls, and to respond to state changes for calls such as from a dialing state to a connected state. Such state changes are known as cellular call events.

The purpose of CTCallCenter is to give the developer the opportunity to pause his app state during a call in order to give the user the best experience.


First, we will define a new class member inside the class we want to handle the interceptions:

@property (atomic, strong) CTCallCenter *callCenter;

Inside our class init (constructor) we will allocate new memory for our class member:

[self setCallCenter:[CTCallCenter new]];

Afterwards, we will invoke our new method that actually handles the interceptions:

- (void)registerPhoneCallListener
[[self callCenter] setCallEventHandler:^(CTCall * _Nonnull call) {
    NSLog(@"CallEventHandler called - interception in progress");

     if ([call.callState isEqualToString: CTCallStateConnected])
     else if ([call.callState isEqualToString: CTCallStateDialing])
     else if ([call.callState isEqualToString: CTCallStateDisconnected])

     } else if ([call.callState isEqualToString: CTCallStateIncoming])

That’s it, if the user will use your app and will receive a phone call you could intercept this call and handle your app for a save state.

It is worth mentioning that there are 4 call states you can intercept:



Define your class member at the relevant class and define it:

self.callCenter = CTCallCenter()
self.callCenter.callEventHandler = { call in
    //  Handle your interception
    if call.callState == CTCallStateConnected

What will happen if your app is in the background and you need to intercept calls while the app is in the background ?

For example, if you develop an enterprise app you can basically just add 2 capabilities (VOIP & Background fetch) in the Capabilities tab:

Your project target -> Capabilities -> Background Modes -> mark Voice over IP & Background fetch

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