im getting the SIGABRT error each time i build. Im seeing the reason below:
Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key numberEntered.'
-(IBAction)numberEntered:(id)sender
{
NSNumber *day=[NSString stringWithFormat:#"#%", dayEntry];
NSLog(#"%#", day);
}
I assume its something to do with me trying to pass the wrong value to *day, but i cant see what the issue is (no errors in xCode).
Essentially all i want to do is to retrieve a Numerical value from a textfield and set it do a variable (day) so i can use it in a calculation. I have added the NSLog in order to ensure im acquiring the correct data from my textfield.
Thanks in advance!
The other problem is your format string and the fact that you are assigning an NSString to an NSNumber.
NSNumber *day=[NSString stringWithFormat:#"#%", dayEntry];
Try to change it to:
NSString *day=[NSString stringWithFormat:#"%#", dayEntry];
Subtle difference, see if you can spot it.
Make sure your custom class implementation implementing numberEntered: (subclassed UIView / UIViewController / UITextFIeld or whatnot) is actually selected within the InterfaceBuilder under Custom Class, Class.
For the sake of this example, I am assuming it is a UIViewController based class and you call it MyViewController. In that sense, you will need to enter that name under the mentioned IB when observing the "File's Owner".
For validating if this actually was your problem, you could add something to your viewDidLoad method that prints something into the console. Before being able to do so, you would have to remove that custom method from the event (as that baby would trigger the exception). If that something does not appear when showing the view of that viewController, you know that you have the described issue.
See this:
try this out :
NSNumber *day = [NSNumber numberWithInt:[dayEntry intValue]];
Make sure, that you actually have registered the method named numberEntered: (note the trailing colon) with IB. It's a method different from numberEntered (without the trailing colon). The error might be caused by
the view calling numberEntered (instead of numberEntered:)
the runtime trying to resolve the (undefined method) via KVC lookup.
This could be caused by a missing (or wrong) File's Owner resp. Custom Class defined in a .xib file for your control (hinted at by Till) or a plain old typo (missing the trailing :).
Related
I have got information from a URL(JSON); I easily populate my tableView with the text from my dictionary [aCategory objectAtKey:#"names"] for the cell labels. Now, based on the cell name (category), I want to display another table that will ask for the last URL in order to grab the rest of the text, based on that category.
So, i want an ID which is in [aCategory objectAtKey:#"ID"] to save to a string and put in the URL in the next viewController. I am currently trying to generate it using the auto-generated set method to populate the NSString *ID in the target viewcontroller; when i call
[newView setID: [aCategory objectAtKey:#"ID"].
My new view controller's NSString ID says it is not empty, but when i try to check to see if it is indeed "1" or "2" i get something like /p2002 or something. However, in the original class, if i say cell.detailLabelText.text = [aCategory objectAtKey:#"ID"];, the labels correctly show "1" "2" "3".."14" etc....
SO, how can i get that ID from that key into my other viewcontroller class?
I Know it is a valid NSCFString cause i tested it both with isClass AND with the cell's detailLabelText.
I need more detail to be sure about this, but a couple of notes...
NSString is what is called a class cluster, which basically means it is actually a collection of several class different classes that the underlying framework switches between...this means if you are checking it with
isKindOfClass:
you might not be getting the results you are expecting. Check the documentation for isKindOfClass: in NSObject.
However, I am not sure if there is anything to worry about. The reason you are seeing something like '\p2002' (Could the first letter be a u?) could just be the current underlying representation of the string. Sometimes, when the device holds the content of the string in memory, it does not look exactly like "1" or "2". It doesn't mean that there is a problem: it just means that, a deeper level, the way the string is being held in memory is in different form. That is why your label might say "2" but the variable, when you check it in memory, looks different.
(I am guessing that, since you are handling JSON, the string is encoded in a form called UTF-8.) The point is, nothing may wrong at all.
The real question is, is your new view controller loading correctly or not? Maybe in the viewDidLoad: method of your new view controller, if you run something this line:
NSLog(#"%#", stringID);
This will print the value of stringID to the console. If this number is the same as the number of the table cell's label in the previous view controller, everything should have been passed correctly.
I have a console message that appears to be triggered by apparently unrelated events.
The message states:
snarfed from ivar layout: [propertyName] = [constantString]
Where [propertyName] is the name of a property to which I set the value of a string constant [constantString].
What causes this message and what does it means?
I also ran into this issue recently. I was able to fix my specific issue, but I don't think that is exactly what the questioners are running into, since my issue was only being exposed in VoiceOver mode. As such, I'll offer thoughts on what I think is generally occurring and then I'll speak to my specific issue.
As for the general issue, I think that the Apple Framework is deciding to look through all of the ivars of a particular class in order to extract some information that it wants, but that is not provided by other parts of the UI element. This seems a little bizarre to me, but that is what I encountered.
So, to continue with the general case, and in answer to the initial question. If you're like me, then your property name is probably the same as your ivar. Try explicitly defining a getter method for that property. Then, set a breakpoint within that getter if you will be returning a non-nil value. Look at the stacktrace and that should tell you which piece of the apple frameworks is deciding to loop through your ivar layout in order to get the information it wants. (If you're not using the the same name for your property and ivar, then just define a property and getter with the ivar name and do the same thing with the breakpoint.)
My specific case was for a Custom Table Cell (like one of the commenters). In that cell,I had a property that was the same name as its ivar. I also had an explicitly defined getter for that property. I also referenced that custom table cell from the Nib file. So, it looked something like this:
class CustomTableViewCell:UITableViewCell
{
NSString *s ;
}
#property(nonatomic,retain) NSString *s ;
and in the implementation:
#synthesize s ;
-(NSString *)s
{
if( !s )
return self.reuseIdentifer ;
return s ;
}
I put a breakpoint in the return self.reuseIdentifier line,and that showed me a stacktrace from the Accessibility functions. The stacktrace showed my method being called by an Apple internal method that was looping through all of my ivars looking for something to use as the accessibilityLabel for my table cell. The name of the selector is '_accessibilityRetrieveTableViewIvarsText'.
To make matter worse, in my case, this was not just a debugger issue, it was messing up my Accessibility interface by using the wrong thing as the accessibilityLabel.
I came up with 3 fixes for my specific problem:
1) I added a value for the accessibilityLabel for the table cell inside the Nib. This satisfied the Apple framework to the point where it did not go searching through my ivars. This was not the solution I went with, however, because I did not want a static accessibility label.
2) I subclassed my CustomTableViewCell with an empty implementation and interface, and I used that as my Table cell class inside the Nib. This solved the problem because the Apple Framework looped through that class's ivars, of which there were none, and there weren't any values to 'snarf'. I did not use that solution either, but it might be the best one because it keeps Apple's frameworks from inspecting my ivars.
3) The solution I decided on was to make my ivar private and to define the property with a different name. That seems to be the standard way that a lot of folks use properties. This is what it looks like:
class CustomTableViewCell:UITableViewCell
{
#private
NSString *_s ;
}
#property(nonatomic,retain) NSString *s ;
and in the implementation:
#synthesize s = _s ;
-(NSString *)s
{
if( !_s )
return self.reuseIdentifer ;
return _s ;
}
This fixed the problem because nil is returned when Apple inspects the ivar, and, thus, nothing is 'snarfed'. I'm still not sure whether this or #2 is more appropriate.
"snarfed from ivar" basically autofills your accessibilityLabel. If you do that yourself, the message goes away, as there is no more need for sneeking into your UITableViewCell.
For future reference. The message is logged by the accessibility framework, which apparently looks through an UIView ivars for strings.
If you have a custom subclass you can define the custom attributes as specified in the following link:
Accessibility Programming Guide
Alternatively you can make the view subclass not accessible:
- (BOOL)isAccessibilityElement
{
return NO;
}
However, note:
If your application contains a custom individual view with which users need to interact, you must make the view accessible.
I'm working on iPhone and I'm using navigation.
I have list of data in RootViewController, and pass one data to detailViewController when a cell is clicked. Like this,
detailViewController.message = [tableData objectAtIndex:indexPath.row];
And I want to modify the content of 'message' in detailViewController. Is that possible?
I've tried that, but I get an error that it's immutable object. How can I do that? Somebody give me a hint. Thanks ;)
Added ------------------------------------------------
Ok. I'll specify the question.
in detailViewController, the message is decleared NSMutableDictionary* type.
and used like this.
NSMutableString *str = [m_message objectForKey:KEY_CONTENT];
[str appendFormat:#"appended!"];
And I've got this message.
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attempt to mutate immutable object with appendFormat:'
Can't I just modify it's content like modifying data in c++ using pointer?
I think it would be best to use a delegate pattern for this. Create a DetailViewControllerDelegate protocol that informs its delegate of a changed message. Something along the lines of:
-(void)detailViewController:(DetailViewController *)controller didChangeMessage:(NSString *)message;
You could also directly manipulate the object by using a mutable one (NSMutableString, NSMutableArray etc.), but using a delegate improves reusability and decouples your classes.
EDIT:
The fact that your dictionary is mutable doesn't mean the object inside it are mutable as well. Your string str is probably immutable. Since NSMutableString is a subclass of NSString, the assignment will work though. You should make sure that you put a mutable string in the dictionary, or use the mutableCopy method of NSString to get a mutable copy of it.
It depends on what type of object you are passing. Immutable means that you cant alter the object. If you for exaple use NSArray, you have to switch to NSMutableArray instead. The same for string or dictionary.
Okay, i think i figured it out. The documentation for appendFormat says that appendFormat is for appending objects, just like when you use stringWithFormat.
The documentation states that:
The appended string is formed using
NSString's stringWithFormat: method
with the arguments listed.
You should use appendString to get the result you want.
I'm a c++ programmer new to objective-c.
I created a calculator app that is working fine using a single view. I have a Calculations class and a ViewController. Every time a button is pressed, an IBAction method in the ViewController calls methods defined in the Calculations class to handle the input and returns the output as an NSString which I then set as the value of the label.text field.
Now I am working on a tab bar app using the same Calculations class. This app has two tabs, each with a unique set of input buttons for the calculator (both views sharing the same input/output data). The first tab is identical to my first app with the single view, so I am trying to do this in a similar fashion.
Here is the problem:
When a button is pressed, the IBAction method that handles the input runs through the calls to the Calculations class methods (shown below) without error:
-(IBAction)readInput:(id)sender {
[_calculations input:[sender titleForState:UIControlStateNormal]];
inputField.text = [_calculations inputDisplay];
outputField.text = [_calculations outputDisplay];
}
however, both the inputDisplay and outputDisplay methods return nil. Using the debugger I noticed that I am unable to "step into" the calls to _calculations methods, instead the line is skipped and the value returned by both is nil. I added the following method:
-(IBAction)setNumber:(id)sender {
NSString *button =(NSString *)[sender titleForState:UIControlStateNormal];
inputField.text = button;
}
and if I attach this to the input buttons I can see the display updated. This seems to be an issue with calling the _calculations member functions and tab bar views (because this issue is not present using a single view).
I realize that I left out a lot of information, but I did it to avoid providing irrelevant information. I will provide all details that are necessary if asked.
Check to make sure _calculations is not nil.
You can send any message (call any method) on nil and it will just return nil, not cause an exception.
Without seeing more code it is going to be a bit difficult to diagnose.
If I was trying to debug this issue I would first make sure _calculations points to the object you want it to point to. If its loaded from a NIB then it might not be getting initialised, and still be nil. You can send messages to nil objects without any issues. If an object receives a message that it cant handle (the method doesn't exist, or the target object is nil) then the return for that call will be nil.
I have in the past put initilization code into the init: method, and spent a few hours why it wasn't being called, until it dawned on me that I needed to put my init code into the viewDidLoad:, or the initWithNibName:bundle: or even the initWithCoder: selector.
HTH, Matt
I'm very new to cocoa touch and am stuck on a problem that doesn't seem to have a google solution. I have added a view to my application, and this view has a button on it. When the button is pressed I want the callback to perform an operation.
My problem is that the callback isn't being called. I created the view in Interface Builder, connected the touch-up-inside connection to my Owner class (in this case a viewController class), and selected the appropriate callback.
The error I get is as follows:
2009-10-13 17:13:51.708 MyApp[7467:20b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[NSCFSet contactsButtonPressed:]: unrecognized selector sent to instance 0x4c27330'
As I understand it this suggests that the connection between contactsButtonPressed and MyViewController is wrong. I'm not sure where the NSCFSet object comes from.
Does anyone have any idea?
Thanks!
The error I get is as follows:
2009-10-13 17:13:51.708 MyApp[7467:20b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[NSCFSet contactsButtonPressed:]: unrecognized selector sent to instance 0x4c27330'
You're probably under-retaining whatever controller object of yours is supposed to receive that action message. Add an NSLog call in the controller's dealloc method; you'll probably find that it gets deallocked before you expect it to.
The question to ask then is what should own that controller. Then, make sure that all of the owners are retaining it.
If you're holding the controller in a property, make sure that you actually use that property. A common mistake is to write myController = theController, which bypasses the property and assigns directly to the instance variable, instead of self.myController = theController (property access syntax, implicit accessor message) or [self setMyController:theController] (explicit message syntax).
Also, if you've implemented your own accessors for the property (especially setMyController:), make sure your setter releases the old object and retains the new one. Of course, this is assuming you have a reason to implement your own accessor; normally, you should simply #synthesize the property and let the compiler write the accessor for you.
somewhere in your code you have a line that looks like this:
[button addTarget:self action:#selector(contactsButtonPressed:)];
If you have a line that looks like this, you will also need to have a method with this signature:
- (void)contactsButtonPressed:(UIButton *)sender {
...
}
If you look at the error, it seems that you are sending the message to an NSCFSet object instead of the controller. I would check that you are setting delegate to self or the controller.
I'm new to cocoa too,
Maybe you forgot to add the sender parameter to your contactsButtonPressed.
Is your view's class named NSCFSet?
Try pasting some code.