Flipping a UISwitch with an NSTimer - objective-c

Question

I'm trying to learn how to use NSTimers, and I thought of the following: Create a switch. Let the timer begin as the app begins, and after each second, a function that changes the state of the switch is called.
Here's what I did so far:
I declared both the timer and the switch in the header file ViewControl.h:
//Timer
{NSTimer *timer;}
#property (weak, nonatomic) IBOutlet UISwitch *zeSwitch;
Then, in the ViewControl.m file I defined the following:
- (IBAction)zeSwitch:(id)sender {
UISwitch *zeSwitchSatus = (UISwitch *) sender;
BOOL yn = zeSwitchSatus.isOn;
[zeSwitch setOn:yn animated:YES];
}
- (void)viewDidLoad
{
timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self
selector:#selector(zeSwitch) userInfo:nil repeats:YES];
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
So my hope was that when I run the code, I'll see a switch that is on or off. Then I'll see it changing its status automatically with time, without me interfering.
But that didn't work! I first get the image above. Nothing changes. Then it crashes when I press the switch. (But my idea is not to touch it at all.)
Any ideas?

Answer 1

You're pretty close. There's a few things wrong here. First, the method that you're giving to the timer is named zeSwitch: -- the colon is significant. So you need to create the timer like this:
timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(zeSwitch:)
userInfo:nil //^ Note colon!
repeats:YES];
The method named zeSwitch without the colon is actually the accessor method for the switch, because you've named your property zeSwitch. You should really rename the timer's action method to clarify this. Right now, the timer is calling the accessor method for the switch every second, which doesn't really do anything.
Next, the timer passes itself to the method it calls. The sender argument in zeSwitch: is going to be the timer, not the switch. If this method was actually being called via the timer, you would get a crash because you'd be sending isOn to the timer, and it doesn't respond to that.
You've got an outlet to the switch, so you can refer to it via that outlet:
- (void)flipSwitch: (NSTimer *)tim
{
BOOL switchIsOn = [[self zeSwitch] isOn];
Notice that I've corrected the names and types in this method -- you'll also need to change the timer creation to reflect this: #selector(flipSwitch:).
Third, you want to flip the switch, so you should be setting it to the opposite of its current status. The next line needs to be:
[[self zeSwitch] setOn:!switchIsOn animated:YES];
The ! operator negates the BOOL to which it's attached, turning YES into NO and vice versa.

Answer 2

1) When you specify a selector that takes one parameter, you need a colon after the name, so #selector(zeSwitch:).
2) The selector that is triggered by a timer gets the timer as a parameter, not a switch, so - (IBAction)zeSwitch:(NSTimer *)timer.