Should I use IBAction with everything that might happen on the screen? - ios

Question

When I created a UISwitch element in my storyboard, and attached it to the .h file, there was this line generated in the controller:
#property (weak, nonatomic) IBOutlet UISwitch *wantHelp;
And I was trying to figure out how to make the system notice when the value was changed, so I tried to manually add something like this below the original statement:
- (IBAction)wantHelp:(id)helpToggle;
and in the controller, I have something like this:
-(IBAction)helpToggle:(id)sender
{
NSLog(#"sender is: %#", sender);
if (wantHelp.on)
{
NSLog(#"yes");
}
else
{
NSLog(#"No");
}
}
What I wanted to do is connect the helpToggle IBAction with the particular UISwitch element, but when I run it, I get an error: unrecognized selector sent to instance which as I understand is means that I called an operation on an incorrect object.
Could someone help me understand what I am doing wrong here?
Thanks!!
This is how my .m file looks like:
#interface PlanBusinessController ()
#end
#implementation PlanBusinessController
#synthesize businessDescription;
#synthesize personName;
#synthesize personEmail;
#synthesize privacy;
#synthesize wantHelp;
-(IBAction)helpToggle:(id)sender
{
NSLog(#"sender is: %#", sender);
if (wantHelp.on)
{
NSLog(#"yes");
}
else
{
NSLog(#"No");
}
}

Answer 1

What's happening is that your UISwitch has been told to call wantHelp: however as no method called this exists in you implementation file (.m file) that is why the 'unrecognized selector sent to instance' error is being called.

Answer 2

So you can have as many IBAction as you want or one it doesnt matter. What matters most is declaring it in your .h file, going into interface builder and linking the desired action to that IBAction.
so you have your IBAction
-(IBAction)WHATEVERNAME:(id)sender
then go to interface builder and click on your File's Owner object(kinda top left). then click on the Connections Inspector (top right)
and drag from the dot where it says WHATEVERNAME to your object (UISwitch wantHelp)
when you do that it will ask you what action you want to receive
take in mind the reason for (id)sender is that you are suppose to cast your object
UISwitch * tempSwitch = (UISwitch*) sender;
so that you have a pointer to the switch object
this is because you could have this same IBAction method handle many different types of objects
although this is all good stuff the actual error came from multiple selectors being called. Once we got into the connection inspector we were able to see the 2 different methods being called by it. One was the valid IBAction and the other was a previously declared method wantHelp

Answer 3

Okay so all the answers failed to give you "the easy way"
Hold down control on your UISwitch and drag it to your .h file.
You will then see a dialog box which will allow you to select the "Connection"
This connection determines if you are creating and IBOutlet or an IBAction.
Once you change it to "Action" you will then have it automatically select "ValueChanged" as the event, and you can give it whatever name you want:
I named it helpSwitchToggled. Then you will have your IBAction in the .h, and in the .m files.
In your .m file you can then write your code for the value changed action:
for copy paste:
- (IBAction)helpSwitchToggled:(id)sender {
if(self.helpSwitch.on)
{
//Do the On stuff
} else {
//Do the Off Stuff
}
}
That is "The easy way" to make an action associated with something on your interface.
The difference between IBAction and IBOutlet has been pointed out in other answers, but basically Actions are responses to control events and Outlets are connections to elements within the view.

Answer 4

IBAction is merely a tag to let Interface Builder know it can attach to that action.
IBAction is defined as void but with the name Interface Builder allows you to drag your connection over it and connect an event from an object to that function.
Other than that Your actions should have meaningful names. helpToggle seems to me to be an on off switch. but usually I would include a bit of description in that message as well. Such as
- (IBAction) helpSwitchToggled:(id) sender{
}
this message gives you a very meaningful name and reading it will tell you exactally what is calling it as well as the type of message that object is sending.
In conjunction I would also have an IBOutlet for that switch called helpSwitch, Like this one.
#property (nonatomic, weak) IBOutlet UISwitch *helpSwitch;
as you can see. that object is clearly a switch. And IBOutlet is actually defined as nothing. but it again is a tag that Interface Builder uses to know you have a property that can be linked to with Interface Builder.
IBAction and IBOutlet are nothing more than Metadata that tells the Interface builder that this is a possible connection. Connecting them is up to you and the compiler treats them like nothing.
I hope this information helped you :)