NSInvalidArgumentException when calling selector with arguments - objective-c

Question

I'm trying to execute a method using selector with one NSString as parameter and fails. I have seen many questions (and answers) like this and tried most solutions but had no success. Please see code and errors below:
My MainView.m is my view controller and it has a method:
-(void)displayMessageOnTextView:(NSString *)message
{
[tv1 setText:message];
}
And in MainView.h:
#interface MainView : UIViewController {
UITextView *tv1;
}
-(void)displayMessageOnTextView:(NSString *)message;
....
I have another thread which is fired by MainView (this is from MainView.m):
- (void) runTest
{
MyThread *t = [[MyThread alloc] initWithInt:13253];
[t setMainView:self];
[t run];
[t release];
}
and MyThread.m:
#import "MyThread.h"
#import "MainView.h"
#implementation MyThread
MainView *_view;
-(id)initWithInt:(int)someInt{
_view = NULL;
return self;
}
-(void)setMainView:(MainView*)view
{
_view = view;
}
-(int)run{
NSString *s = [NSString stringWithFormat:#"Display on Gui:%d", 1];
[_view performSelectorOnMainThread:#selector(displayMessageOnTextView:message:) withObject:s waitUntilDone:YES];
}
#end
Error:
2011-04-20 02:08:11.553 myApp[22627:207] -[MainView displayMessageOnTextView:message:]: unrecognized selector sent to instance 0x4e383a0
2011-04-20 02:08:11.555 myApp[22627:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[MainView displayMessageOnTextView:message:]: unrecognized selector sent to instance 0x4e383a0'
*** Call stack at first throw:
(
0 CoreFoundation 0x00dc55a9 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x00f19313 objc_exception_throw + 44
2 CoreFoundation 0x00dc70bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3 CoreFoundation 0x00d36966 ___forwarding___ + 966
4 CoreFoundation 0x00d36522 _CF_forwarding_prep_0 + 50
5 Foundation 0x0079e94e __NSThreadPerformPerform + 251
6 CoreFoundation 0x00da68ff __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
7 CoreFoundation 0x00d0488b __CFRunLoopDoSources0 + 571
8 CoreFoundation 0x00d03d86 __CFRunLoopRun + 470
9 CoreFoundation 0x00d03840 CFRunLoopRunSpecific + 208
10 CoreFoundation 0x00d03761 CFRunLoopRunInMode + 97
11 GraphicsServices 0x00ffd1c4 GSEventRunModal + 217
12 GraphicsServices 0x00ffd289 GSEventRun + 115
13 UIKit 0x00025c93 UIApplicationMain + 1160
14 myApp 0x000024c9 main + 121
15 myApp 0x00002445 start + 53
)
terminate called after throwing an instance of 'NSException'
NOTE:
I'm new to Objective-C (and generally iOS) programming, so any comment regarding coding conventions and best practice will be appreciated (even if not related to my question, but related to my code)

Answer 1

Your method has been declared as
-(void)displayMessageOnTextView:(NSString *)message;
This means that the method name is displayMessageOnTextView: and the corresponding selector is #selector(displayMessageOnTextView:). Note that a method name does not include parameter (variable) names.
In your -run method, change
[_view performSelectorOnMainThread:#selector(displayMessageOnTextView:message:)
withObject:s
waitUntilDone:YES];
to
[_view performSelectorOnMainThread:#selector(displayMessageOnTextView:)
withObject:s
waitUntilDone:YES];
and that runtime error shouldn’t happen again.
For the record, a method declaration corresponding to displayMessageOnTextView:message: would be:
- (void)displayMessageOnTextView:(type1)parameter1 message:(type2)parameter2;

Answer 2

This method:
-(void)displayMessageOnTextView:(NSString *)message
has the selector displayMessageOnTextView:. The name of the parameter itself (message in your case) does not appear in the selector. (This should be sort of intuitive: the name doesn't necessarily appear when you call the method, so it doesn't appear in the selector.) So you need to be using #selector(displayMessageOnTextView:).