I released my first solo iPhone app last week that calculates 12V Marine and Boat Battery usage. I had tested it vigorously on the simulator and on my iPhone, and when I was comfortable all was well, I archived the app and released it to Apple. When users started using the app, they noted a calculation was not working as expected. The below code, which is a method on a NSManagedObject model, was producing a DIFFERENT output when released to when in debug.
The below should sum up the total of the related Discharge items - but if there are no BBDischarge items, then it should return zero. Instead, when there are no items (thus the for loop doesn't fire) it returns a figure that is the direct product of the domesticAH (an NSNumber). If I set the domesticAH to 100, the below dischargeAH returns 8, if set the domesticAH to 1000, it returns 83 (the float is rounded when it is displayed). Again, I stress the below works fine when running on the simulator, or put directly onto my iPhone 4s, only once released through the app store does it screw up.
//Other dynamics hidden for simplicity
#dynamic domesticAH;
#dynamic voltage;
#dynamic profileDischarge;
-(NSNumber*) dischargeAmpH
{
float totalWattsPD;
//Calculate the watts per day so we can accurately calculate the percentage of each item line
for(BBDischarge* currentDischarge in self.profileDischarge)
{
float totalWatt = [currentDischarge.wattage floatValue] ;
float totalMinsPD = [currentDischarge.minutesPD floatValue]/60;
float totaltimesUsed = [currentDischarge.timesUsed floatValue];
float numberInOperation = [currentDischarge.number floatValue];
totalWattsPD = totalWattsPD + ((totalWatt * totalMinsPD) * (totaltimesUsed * numberInOperation));
}
int voltage = ([self.voltage integerValue] + 1) * 12;
float totalAmpsPD = totalWattsPD / voltage;
return [NSNumber numberWithFloat:totalAmpsPD];
}
As you can see, self.domesticAH is not featured in the method anywhere, and as I can't recreate this in the simulator, I am having a hard time tracking this down.
A few questions:
Can I debug the live version of my app? Attach XCode to my running, App Store downloaded instance of my app?
Is there a way I can simulate an install from the archive - would anyone recommend ad hoc distribution to do this? I havent used ad hoc yet.
Any other ideas why this might be behaving in this way?
Is more a hint than an answer.. but, as I already said in comments: you can check the different behavior between Release and Debug version.
This different "behavior" has been seen in the past. Is given by "Optmization Level" setting. Debug version is set to None [-O0], while the Release version is set to Fastest, Smallest [-Os].
An example here .. here another ..
Related
There are a few questions on this already, but nothing in them seems to provide accurate results. I need to determine simply if the phone is connected to a cell network at a given moment.
http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Reference/CTCarrier/Reference/Reference.html
This class seems to be documented incorrectly, returning values for mobileCountryCode, isoCountryCode and mobileNetworkCode where no SIM is installed to the phone. carrierName indicates a 'home' network or a previous home network if the phone has been unlocked.
I also looked up and found some people claiming the following to work, which uses an undocumented method of the CoreTelephony framework, but the results have been useless to me, reporting seemingly random figures, where perhaps it is not itself updating consistently.
-(int) getSignalStrength
{
void *libHandle = dlopen("/System/Library/Frameworks/CoreTelephony.framework/CoreTelephony", RTLD_LAZY);
int (*CTGetSignalStrength)();
CTGetSignalStrength = dlsym(libHandle, "CTGetSignalStrength");
if( CTGetSignalStrength == NULL) NSLog(#"Could not find CTGetSignalStrength");
int result CTGetSignalStrength();
dlclose(libHandle);
return result;
}
Thanks.
Edit: The app is connected to an internal wifi and must remain so, making a reachability check more difficult.
I'm playing with this function and I've noticed you're calling it in an interesting way. I'm calling it by adding CoreTelephony.framework as a compile-time link. For the function itself, you'll want to declare it's prototype somewhere (perhaps immediately above the method you call from):
int CTGetSignalStrength();
This needs to be declared since it isn't in a public header for CoreTelephony.
Now, I built a simple app that prints signal strength every second.
int CTGetSignalStrength();
- (void)viewDidLoad
{
[super viewDidLoad];
while (true) {
printf("signal strength: %d\n", CTGetSignalStrength());
sleep(1);
}
}
I ran it on my iPad mini and it shows steady values until I picked it up, where the number went up. Wrapping my iPad in tin foil (tin foil is a debugging tool I have never used before) caused the number to go down. When I put my iPad in airplane mode, it kept repeating the last value, so this will not be an accurate measure for you.
If you want to test if a device currently has a cellular data network connection, you may be more interested in Reachability, specifically kSCNetworkReachabilityFlagsIsWWAN.
Ok I think I have the correct solution now, which was a bit simpler in the end.
The issue with the CTGetSignalStrength() method is that it works normally, but if you remove a sim, it reports the last signal before the removal. I found another method in the same framework called CTSIMSupportGetSIMStatus(), also undocumented, which can tell you if a SIM is currently connected. Using both as follows should confirm the current network signal.
First declare the methods:
NSString * CTSIMSupportGetSIMStatus();
int CTGetSignalStrength();
Then check connectivity to cell network like so:
NSString *status = CTSIMSupportGetSIMStatus();
int signalstrength = CTGetSignalStrength();
BOOL connected = ( [status isEqualToString: #"kCTSIMSupportSIMStatusReady"] && signalstrength > 0 );
I have been using mach_absolute_time() for all my timing functions so far. calculating how long between frames etc.
I now want to get the exact time touch input events happen using event.timestamp in the touch callbacks.
the problem is these two seem to use completely different timers. sure, you can get them both in seconds, but their origins are different and seemingly random...
is there any way to sync the two different timers?
or is there anyway to get access to the same timer that the touch input uses to generate that timestamp property? otherwise its next to useless.
Had some trouble with this myself. There isn't a lot of good documentation, so I went with experimentation. Here's what I was able to determine:
mach_absolute_time depends on the processor of the device. It returns ticks since the device was last rebooted (otherwise known as uptime). In order to get it in a human readable form, you have to modify it by the result from mach_timebase_info (a ratio), which will return billionth of seconds (or nanoseconds). To make this more usable I use a function like the one below:
#include <mach/mach_time.h>
int getUptimeInMilliseconds()
{
static const int64_t kOneMillion = 1000 * 1000;
static mach_timebase_info_data_t s_timebase_info;
if (s_timebase_info.denom == 0) {
(void) mach_timebase_info(&s_timebase_info);
}
// mach_absolute_time() returns billionth of seconds,
// so divide by one million to get milliseconds
return (int)((mach_absolute_time() * s_timebase_info.numer) / (kOneMillion * s_timebase_info.denom));
}
Get the initial difference between two i.e
what is returned by mach_absolute_time() initally when your application starts and also get the event.timestamp initially at the same time...
store the difference... it would remain same through out the time your application runs.. so you can use this time difference to convert one to another...
How about CFAbsoluteTimeGetCurrent?
I'm looking for a reliable way to get the time. It can't be tampered with and it needs to work offline. So no internet time , no user time setup in settings and no BSD uptime time since last reboot. I was wondering since GPS works using atomic clock, whether I could access that information.
Thank you
This works to get the GPS time:
#import <CoreLocation/CoreLocation.h>
CLLocation* gps = [[CLLocation alloc]
initWithLatitude:(CLLocationDegrees) 0.0
longitude:(CLLocationDegrees) 0.0];
NSDate* now = gps.timestamp;
It doesn't seem to be tamper-proof though.
I tried this code on an iPhone 4 in airplane mode (iOS 6.1), and even then it gives a time all right. But unfortunately this time seems to change with the system clock. Ugh.
Funny thing that I found (still in airplane mode) is that if you tamper with the system clock (after turning to off Time & Date's Set Automatically), and then turn Set Automatically back to on, the machine restores the real (original) time without a hitch. this works even after cycling the phone's power. So it seems that there is something like a tamper-proof time the device maintains internally. But how to access this?
P.S. A discussion of this from 2010. The author of the penultimate comment tried this in a fallout shelter: so it's clear the phone is not getting the pristine time from any external source.
Addendum, July 2013
Found a few more posts (here, here and here) about another kind of time measure: system kernel boot time. It's accessed through a call something like this: sysctlbyname("kern.boottime", &boottime, &size, NULL, 0);. Unfortunately it too changes with the user-adjusted data and time, even without reboot. Another function gettimeofday() is similarly dependent on user-defined time.
NSDate and it's CF counterpart are all based on the user controllable time, and thereby aren't tamper proof.
As far as I know, there is no open API for either GPS time or carrier time directly. However, you can check the mach_absolute_time to get untampered time since last boot up, and perhaps use it to at least be aware of how much time has passed since the app has been awoken (without having the potential for that time to be tampered with while the app is running).
mach_absolute_time depends on the processor of the device. It returns ticks since the device was last rebooted (otherwise known as uptime). In order to get it in a human readable form, you have to modify it by the result from mach_timebase_info (a ratio), which will return billionth of seconds (or nanoseconds). To make this more usable I use a function like the one below:
#include <mach/mach_time.h>
int getUptimeInMilliseconds()
{
static const int64_t kOneMillion = 1000 * 1000;
static mach_timebase_info_data_t s_timebase_info;
if (s_timebase_info.denom == 0) {
(void) mach_timebase_info(&s_timebase_info);
}
// mach_absolute_time() returns billionth of seconds,
// so divide by one million to get milliseconds
return (int)((mach_absolute_time() * s_timebase_info.numer) / (kOneMillion * s_timebase_info.denom));
}
Even if you can get hold of the time from GPS you should be aware that GPS time is not quite the same as UTC. The GPS receiver in the iPhone might take care of that for you though.
This gets you the current date and time:
NSDate *now = [NSDate date];
This will be as reliable as you can get. The internal clock on the iPhone will be updated when it can get access to an NTP server. If the phone uses GPS as a time sync source it'll also be used to update the same system-wide clock which is accessible via the above method.
The CoreFoundation equivalent is something like:
CFAbsoluteTime now = CFAbsoluteTimeGetCurrent();
Which returns the CoreFoundation equivalent of the normal UNIX seconds-since-epoch timestamp.
The gold standard of timekeeping are the various government time observatories in the U.S. and worldwide. They provide Atomic time. That is used world wide. Apple should be using that. If the want to sync w/ the cell towers, there should be an Alternate internal time. If the tower or GPS system malfunctions all are left with incorrect time.
I'd like to detect from within my app whether the iPhone has been rebooted since last time my app was started. I need to do this because my app uses the timer since last system reboot to clock a user's time and I want to detect reboot so I can invalidate the time.
Is there anywhere I could extract the information from the system console log like reboot , crashes ? The organizer in xcode can access it , maybe I can too.
If not , can you think of other ways to get this information?
This seems like it would work:
get the time since last reboot, and for this example, let's store it in a variable called 'tslr' (duration in milliseconds I guess, BTW, how do you get that?)
get the current time, store it in variable 'ct' for example
compute the last reboot time (let's call it 'lr'), we have: lr = ct - tslr
store 'lr'
Next time your application gets started, load the previous value for 'lr', compute the new one, and if they differ, you have detected a reboot (you'll probably have to tolerate a small difference there... a couple milliseconds perhaps).
I think it would be pretty tough to fool that... the user would have to tamper their phone time very precisely, and they would have to start your application at a very precise moment on top of that, exactly when the new 'lr' would be identical to the previous one... pretty tough to do, the probability of them being able to do that is very close to 0 I think. And you don't need any internet connection to do that...
The new 'lr' would be identical to the previous one in the following cases only:
phone was not rebooted, and time was not changed
time was tampered with, AND the user managed to start your application at the precise millisecond to fool your algorithm (chances of that happening more than ultraslim)
// Returns true if device has rebooted since last time
private func deviceRebootedSinceLastTime() -> Bool {
let userDefaults = NSUserDefaults.standardUserDefaults()
let systemUptime = NSProcessInfo.processInfo().systemUptime;
let timeNow = NSDate().timeIntervalSince1970
let dateOfLastReboot = NSDate(timeIntervalSince1970: timeNow-systemUptime)
var didDeviceRebootSinceLastTime = false
if let storedDateOfLastReboot:NSDate = userDefaults.objectForKey("deviceLastRebootDate") as? NSDate {
if Int(dateOfLastReboot.timeIntervalSinceDate(storedDateOfLastReboot)) < 1 { //
print("Reboot time didn't change - date: \(dateOfLastReboot)");
}
else {
print("Reboot time has changed - from: \(storedDateOfLastReboot) to \(dateOfLastReboot)");
didDeviceRebootSinceLastTime = true
}
}
else {
print("Reboot time is saved for the first time")
didDeviceRebootSinceLastTime = true // first time we save value
}
userDefaults.setObject(dateOfLastReboot, forKey: "deviceLastRebootDate")
userDefaults.synchronize() // don't forget this!!!
return didDeviceRebootSinceLastTime;
}
Zoran's answer is the right way to go; it's the closest you are going to get without a network connection. (neither the cellular subsystem, nor the syslog are accessible for security reasons)
If you are looking to prevent malicious users from generating fake time data, have some central server (or trusted local server for enterprise deployments) track time-related events for you.
Get and save the time either from the iPhone or from NIST and the current runtime from the BSD uptime function. For NIST time see How can I get the real time in iPhone, not the time set by user in Settings?
When you want to check for a reboot get new values of these, compute the elapsed time for each and compare the elapsed times. Based on the difference you should be able to determine a reboot.
Here is one I made. It takes the current time in GMT and the time since last reboot to extrapolate a date for when the device was last restarted. Then it keeps track of this date in memory using NSUserDefaults. Enjoy!
Note: Since you want to check this since last time app was started, you need to make sure you call the method anytime the app is started. The easiest way would be to call the method below in +(void)initialize { and then also whenever you need to check it manually
#define nowInSeconds CFAbsoluteTimeGetCurrent()//since Jan 1 2001 00:00:00 GMT
#define secondsSinceDeviceRestart ((int)round([[NSProcessInfo processInfo] systemUptime]))
#define storage [NSUserDefaults standardUserDefaults]
#define DISTANCE(__valueOne, __valueTwo) ((((__valueOne)-(__valueTwo))>=0)?((__valueOne)-(__valueTwo)):((__valueTwo)-(__valueOne)))
+(BOOL)didDeviceReset {
static BOOL didDeviceReset;
static dispatch_once_t onceToken;
int currentRestartDate = nowInSeconds-secondsSinceDeviceRestart;
int previousRestartDate = (int)[((NSNumber *)[storage objectForKey:#"previousRestartDate"]) integerValue];
int dateVarianceThreshold = 10;
dispatch_once(&onceToken, ^{
if (!previousRestartDate || DISTANCE(currentRestartDate, previousRestartDate) > dateVarianceThreshold) {
didDeviceReset = YES;
} else {
didDeviceReset = NO;
}
});
[storage setObject:#(currentRestartDate) forKey:#"previousRestartDate"];
[storage synchronize];
return didDeviceReset;
}
Ok, the problem is that when my app runs on the simulator it seems to work fine. On the device, however it does not update all the labels. I think the error is somewhere here:
- (IBAction)buttonclick1 {
self.startDate = [NSDate date];
double value = [self Level];
double value2 = [self Level2];
if ((value2 - value) >= 3.0) {
ifWork.text = #"DONE!";
ifWork.textColor = [UIColor yellowColor];
float noSeconds = (float) [self.startDate timeIntervalSinceNow];
}
}
I am new to this game. What I am looking for, is when the button is pressed, it times how long it takes for an event to happen. I then would like to use this time in calculations.
I know the IF statement is correct as it works on the simulator. However on the device, when value and value2 differ by 3 and then the button is pressed, nothing happens (the label ifWork doesn't change!).
Any help would be much appreciated,
Stu
Did you run the code in the debugger to see what happens? Maybe if the values depend on anything like CPU or network performance you may experience notable differences between the simulator and the actual device, so you cannot be sure that what works on the simulator works on the device.
There could be a few reasons.
Level1 or Level2 results could be different on device (using uninitialized memory which is different on device
value2 - value1 could be very close to 3.0 but just less than (doubles are often a little imprecise)
ifWork could be improperly set on the device (i.e. nil) so nothing happens.
The best solution is to debug on the device (step over this code line by line) and check if any of these things are true.