respondsToSelector Cannot be Called? - ios

Question

Sorry about the confusion.
What I want to do:
enter a string in a textfield in a view(EnterCommandViewController) and click save button, which will dismiss current view and go back to another view(DetectionViewController) and show the string in the UILabel in current view(DetectionViewController). So I have put define the delegate protocol in EnterCommandViewController, my question is that why the respondToSelector, which is used to check whether someone is listening does not work.
I am really a beginner in iOS, I am right now writing a delegate to send text got form UITextField to a UILabel, But I found that the respondToSelector cannot be called by using NSLog for testing.
Below is my code for reference:
EnterCommandViewController.h
#import <UIKit/UIKit.h>
#import "RscMgr.h"
#protocol EnterCommandDelegate <NSObject>
-(void) commandEntered:(NSString*)command;
#end
#interface EnterCommandViewController : UIViewController <RscMgrDelegate>
{
RscMgr* rscMgr;
__weak IBOutlet UITextField *inputTextField;
__unsafe_unretained id<EnterCommandDelegate> delegate;
}
-(void)sendMessage:(NSString*)message;
- (IBAction)cancelPressed;
- (IBAction)savePressed;
#property (nonatomic,assign)id delegate;
#end
EnterCommandViewController.m
#import "EnterCommandViewController.h"
#interface EnterCommandViewController () <UITextFieldDelegate>
{
#private
BOOL connected;
}
#end
#implementation EnterCommandViewController
#synthesize delegate;
- (void)viewDidLoad {
[super viewDidLoad];
rscMgr = [[RscMgr alloc] init];
[rscMgr setDelegate:self];
// Do any additional setup after loading the view, typically from a nib.
inputTextField.text=#"";
[inputTextField becomeFirstResponder];
}
-(void) viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
inputTextField.delegate = self;
}
-(void) viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
inputTextField.delegate = nil;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)cancelPressed {
[self dismissViewControllerAnimated:YES completion:^{}];
}
- (IBAction)savePressed {
//is anyone listening
NSLog(#"the command is %#",inputTextField.text);
NSLog(#"Checking -- SomeMethod is listening");
if([delegate respondsToSelector:#selector(commandEntered:)]){
NSLog(#"SomeMethod is listening");
//send delegate function with the command entered by the user
[delegate commandEntered:inputTextField.text];
}
[self dismissViewControllerAnimated:YES completion:^{}];
}
DetectionViewController.h
#import <UIKit/UIKit.h>
#import "EnterCommandViewController.h"
#interface DetectionViewController : UIViewController <EnterCommandDelegate>{
__weak IBOutlet UILabel *showCommand;
}
- (IBAction)showSettings:(UIBarButtonItem *)sender;
#end
DetectionViewController.m
#import <Foundation/Foundation.h>
#import "DetectionViewController.h"
#implementation DetectionViewController
- (IBAction)showSettings:(UIBarButtonItem *)sender {
}
-(void) viewDidLoad{
[super viewDidLoad];
showCommand.text=#"";
EnterCommandViewController* enterCVC = [[EnterCommandViewController alloc] init];
enterCVC.delegate = self;
}
#pragma mark - EnterCommandDelegate function(s)
-(void) commandEntered:(NSString *)command{
// showCommand.text = command;
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"command: %#",command);
[self->showCommand setText:command];
});
}
#end
AppDelegate.m
#import "AppDelegate.h"
#interface AppDelegate ()
#end
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
return YES;
}

Answer 1

You are not setting the delegate properly.
EnterCommandViewController* enterCVC = [[EnterCommandViewController alloc] init];
enterCVC.delegate = self;
This is not the way of setting the delegate in your case, since you are not using the created instance of enterCVC, instead a new instance is created from the storyboard when you are transitioning toEnterCommandViewController `(From your comment its clear that you are using the storyboard for this).
So what you can do is you should the delegate from prepareForSegue in DetectionViewController like
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Get reference to the destination view controller
EnterCommandViewController* enterCVC = [segue destinationViewController];
enterCVC.delegate = self;
}