Get a local variable from a function and implement the variable in another function which can be changed dynamically

my app has a function, it gets a value from a NSTextField and then declare the variable, like this:

- (IBAction)startTimer

//all the other code

int totalTime = secs + hoursInS开发者_Python百科econds + minutesInSeconds

timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerHandler) userInfo:nil repeats:YES];

then, i want to use the local variable totalTime in another function which processes the NSTimer.

- (void)timerHandler

//all other code

totalTime =  totalTime - 1;   

//invalidate timer when it reaches 0
if (totalTime == 0.0) {
    [timer invalidate];

however, as the variable totalTime is a local variable, i cannot use the value, and i cannot move the code over as NSTimer calls it every 1 sec and as the user may change the variable (and thus redeclaring it).

so, is there any way i can get a local variable from a function and implement the variable in another function which can be changed dynamically? or can i implement a NSTimer countdown by just using one function

You could wrap the value in the timer's userInfo:

NSNumber *totalTimeNumber = [NSNumber numberWithInt:totalTime];
timer = [NSTimer scheduledTimerWithTimeInterval:... target:... selector:... userInfo:totalTimeNumber repeats:...];

Or just make it an instance variable.

Well, here's a fun one that works with local variables, instead of instance variables but only on Mac OS 10.6/iOS 4 and above:

-(IBAction)startTimer:(id)sender
{
    // ensure, that the variables we'll capture in the block are mutable
    __block int totalTime = ...
    __block NSTimer *timer;
    void (^timerBlock)() = ^{
        if (--totalTime <= 0) { // this comparison is much less fragile...
            [timer invalidate];
        }
    };
    // If you'd call timerBlock() at this point you'll crash because timer contains junk!
    // However, (since timer is declared as __block) we can give it a meaningful value now and have it updated inside of the block, as well:
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerHandler:) userInfo:timerBlock repeats:YES];
}

-(void)timerHandler:(NSTimer*)timer
{
   ((void (^)())[timer userInfo])(); // retrieve the block and run it
}

Caveat:
Since I'm sending this from my phone, I am not 100% sure about the cast in timerHandler:. But it's something along this line... You should be able to omit the cast altogether, but will definitely see a warning then.