Programmatically getting the iPhone's carrier signal strength

Question

Is there a way to get the iPhone's carrier, and/or the current signal strength, using Objective-C? I know how to determine if a data connection is present, and whether or not that connection is wi-fi vs. cellular. I also know that you can manually place the iPhone into "field test" mode by going to the phone app, and dialing #3001*12345*# and hitting Send.

Answer 1

You made me curious and I found out that it's actually *3001#12345#* (hashes and stars exchanged).

Answer 2

This probably won't pass Apple's review, but you can use CTTelephony notifications. First, link against CTTelephony. Now just use this:

static void callback(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo) {

    CFShow(name)

    NSString *sName = name;
    if ([sName isEqualToString:@"kCTIndicatorsSignalStrengthNotification"]) {
        if (userInfo) CFShow(userInfo);
    }    
}

And this to subscribe:

id ct = CTTelephonyCenterGetDefault(); 

    CTTelephonyCenterAddObserver(
                                 ct, 
                                 NULL, 
                                 callback,
                                 NULL,
                                 NULL,
                                NULL);