Change the displayed unit instantly after user changes it using UISegmentedControl - objective-c

Question

I have a UISegmentedControl that handles the setting of the temperature unit (ºC/ºF).
It works correctly but if the user changes the setting, the displayed unit won't change (refresh itself) unless the user navigates to another View Controller and then back to the one in question.
I'm using
- (void)viewWillAppear:(BOOL)animated
{
//Gets user setting choice for Fahrenheit or Celsius
NSUserDefaults *preferences = [NSUserDefaults standardUserDefaults];
temperatureSetting = [[preferences valueForKey:#"temperature setting"]intValue];
//For getting the current value of temperature from the JSON data
NSInteger temp = [[conditions objectForKey:#"temperature"]intValue];
//For checking the user's setting to display either Fahrenheit or Celsius
if (temperatureSetting == 0) {
temp = (temp * 1.8) + 32;
temperatureLabel.text = [NSString stringWithFormat:#"%i°F", temp];
} else {
temperatureLabel.text = [NSString stringWithFormat: #"%iºC", temp];
}
}
- (IBAction)temperatureSelection:(UISegmentedControl *)sender {
//Used to save settings
NSUserDefaults *temperaturePreference = [NSUserDefaults standardUserDefaults];
//To check which segment is selected and save the value but also remember it
if ([sender selectedSegmentIndex] == 0) {
[temperaturePreference setInteger:0 forKey:#"temperature setting"];
[selectedSegment setInteger:0 forKey:#"segment setting"];
} else if ([sender selectedSegmentIndex] == 1) {
[temperaturePreference setInteger:1 forKey:#"temperature setting"];
[selectedSegment setInteger:1 forKey:#"segment setting"];
}
//To make sure the setting is saved
[temperaturePreference synchronize];
[selectedSegment synchronize];
}
How can I make it change the displayed unit instantly after the user changes it?
Thank You!

Answer 1

Move the code inside viewWillAppear: to a separate method. Call that method when the user changes the settings.

Answer 2

Try to add that line of code before the end of - (IBAction)temperatureSelection:(UISegmentedControl *)sender method.
- (IBAction)temperatureSelection:(UISegmentedControl *)sender{
//..etc
temperatureSetting = [[temperaturePreferences valueForKey:#"temperature setting"]intValue];
if (temperatureSetting == 0) {
temp = (temp * 1.8) + 32;
temperatureLabel.text = [NSString stringWithFormat:#"%i°F", temp];
} else {
temperatureLabel.text = [NSString stringWithFormat: #"%iºC", temp];
}
[self.view setNeedsDisplayInRect:temperatureLabel.frame];//probably is not needed it forces the view to redraw itself as it mark as dirty
}