CODEWITHSUNDEEP
objective-cloopstextlabel
John
John

Reputation: 31

Objective C - loop to change label text

i have a loop that looks like this

for(int x=0; x < 10; x++){
    [testLabel setText:[self randomString]];
    sleep(1);
}

The randomString is a method where it returns a random string from an array.

I'm using sleep so it is actually possible to see the label being changed.

The loop works fine but the label only gets updated after the last iteration from the loop.

Does anyone know why this could be? And would there be a way to fix it?

Upvotes: 1

Views: 4879

Answers (4)

Khattab
Khattab

Reputation: 737

It's better if you run your string on a background thread

[self performSelectorInBackground:@selector(updateBusyLabel:) withObject:[NSString stringWithFormat:@"Processing ... %i",iteration]];

-(void)updateBusyLabel:(NSString *)busyText {
    [_busyLabel setText:busyText];
}

I wouldn't use sleep(), and the timer is too much work.

Upvotes: 0

bbum
bbum

Reputation: 162722

Do not call sleep()

Certainly not ever on the main thread and any use of sleep in secondary threads is generally highly questionable.

In this case, just use an NSTimer instance to periodically update the value (as Wilbur said).

Upvotes: 4

CristiC
CristiC

Reputation: 22708

To get updated you should run it separately:

for(int x=0; x < 10; x++){
    [self performSelectorOnMainThread:@selector(updateLabel) withObject:nil waitUntilDone:NO];
    sleep(1);
}

- (void) updateLabel {
    [testLabel setText:[self randomString]];
}

Upvotes: 0

Wilbur Vandrsmith
Wilbur Vandrsmith

Reputation: 5050

The UI is only updated at the end of a run loop, of which your loop is running inside of a single iteration of. You should be using an NSTimer instead.

Upvotes: 3

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