CODEWITHSUNDEEP
objective-ccconditional-statements
Samantha Catania
Samantha Catania

Reputation: 5316

Keep Checking till True

What is the most efficient way to keep checking if a certain something happened & if that something happened you execute a set of commands? (I'm working with C & Obj-C)

Upvotes: 1

Views: 849

Answers (4)

Samantha Catania
Samantha Catania

Reputation: 5316

I found out that it is best is I create a thread that runs in the background until a condition is met

Upvotes: 1

mayuur
mayuur

Reputation: 4746

Use this.

NSTimer *newTimer = [NSTimer timerWithTimeInterval:5 target:self selector:@selector(checkBoolValue) userInfo:nil repeats:YES];

This method will run checkBoolValue after every 5 seconds.

Now, when your boolean value gets set, then stop the timer by

[newTimer invalidate];

newTimer = nil;

Upvotes: 4

Heisenbug
Heisenbug

Reputation: 39174

You can use busy waiting (bad idea because you waste cpu cycles):

while (true){
     if(CheckConditionTrue()){
         doSomething();
     }
}

Better is use select function with a timeout, for example if you are waiting for file descriptor events. With select function you can listen for events happened on given file descriptors. The execution is blocked until an event happen or when the timeout limit is reached.

If you don't or can't use select, use I timeout (still better than busy waiting):

while (true){
    nextTimeInterval();
    //do what you want
}

void nextTimeInterval(){
    sleep (INTERVAL_TO_SLEEP);
    return;
}

Upvotes: 1

Steve Jessop
Steve Jessop

Reputation: 279285

Depends what kind of "certain something". Usually the most efficient is to have the thing that does the "certain something" notify you, using for example a semaphore, a condition variable, or an asynchronous I/O library. Then you just sleep waiting for the notification. What function you need to call to wait depends what kind of notification it is.

Upvotes: 1

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