如何调试“发送到实例的无法识别的选择器”错误

Try setting a symbolic breakpoint on -[NSObject(NSObject) doesNotRecognizeSelector:]. Just click [+] in the bottom left corner of the Breakpoint Navigator to add a breakpoint. Then click 'Add Symbolic Breakpoint'. Reproducing your crash now should give you a better idea where in your code the issue occurs.

The critical first step is to analyze the error message:

[UITableViewCellContentView image]: unrecognized selector sent to instance

This tells you that the "message" image was "sent" to an object of class UITableViewCellContentView. (In other words, an attempt was made to call the method image on an object of class UITableViewCellContentView.)

The first thing to ask is "Does this make any sense at all?" It may be that the named class has an Image method, but not an image method, and so the wrong method name was used on the call. Or it may be that the named method is someMethod:someParm:, but the class implements someMethod:someParm:anotherParm:, meaning that a parameter was omitted on the call.

Most often, though, the named class does not have any method even vaguely resembling the named method, meaning that somehow a pointer to the wrong object was used in the failing call.

For instance, one might do:

NSArray* myArray = [myDictionary objectForKey:@"values"];
NSString* myString = [myArray objectAtIndex:5];

And get an error along the lines of:

[__NSDictionaryI objectAtIndex:] unrecognized selector sent to instance

because the object retrieved from myDictionary was, in fact, an NSDictionary, not the NSArray that was expected.

Most confusing, unfortunately, is when this sort of error occurs deep in UI system code rather than in your own code. This can happen when you somehow passed the wrong object to a system interface, or perhaps configured the wrong class in Interface Builder or wherever.

Another possible reason is that the original object was destroyed and then another object was allocated at the same memory address. Then your code sends the message, thinking it still has a pointer to the old object, and Objective-C throws an exception because the new object doesn't understand that message.

To diagnose this problem, run the Profiler with 'Zombies' detection.

I had the same problem, and this worked for me:

Override the isEqual in your SKScene:

- (BOOL)isEqual:(id)other {


if (![other isMemberOfClass:[SKScene class]]) {
return false;
}
return [super isEqual:other];
}

In these scenarios I've found it helpful to look at two things

1. The call-stack
2. The local variables (and their types) at each stack frame

When I've had this error, it's usually because I sent a message to an instance of Type A, when I was expecting Type B.

In this specific scenario, you may not be satisfying a requirement of a parent class (given your instance of ItemTableViewCell most likely inherits).

Can you maybe show us the code for your ItemTableViewCell class?

You can use the following code to declare the variable:

let noteListTableViewCellobject = "NoteListTableViewCell";` `// Note listTablecell create custom cell`


func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {


var cell:NoteListTableViewCell? = tableView.dequeueReusableCellWithIdentifier(noteListTableViewCellobject) as? NoteListTableViewCell


if (cell == nil) {
let nib:Array = NSBundle.mainBundle().loadNibNamed("NoteListTableViewCell", owner: self, options: nil)
cell = nib[0] as? NoteListTableViewCell
}
}

You can easily track such crashes using Exception Breakpoints.

Open the Breakpoint Navigator and add the

Once you add the Exception Breakpoint, option will be open to choose the Exception.

Select Objective-C.

Run the code and crash the application, breakpoint will stop you to the point where the code is crashing.

You have to pass indexPath to declare object of tableview cell.

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {


let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath)


return cell
}

Swift 5.0

You can use Introspection to find out whether object responds to a particular selector or not..

let canWork = yourObject.respondsToSelector(Selector("image"))   // true

Only if it is true that code will work.. otherwise it will crash for sure