CODEWITHSUNDEEP
iosobjective-ccocoa-touchinheritance
Atma
Atma

Reputation: 29767

ios uiviewcontroller inheritance throws duplicate symbols error

I have a parent view controller with a single method I want available to all child classes:

#import "GAViewController.h"

@interface GAViewController ()<UITextFieldDelegate>

@end

@implementation GAViewController


#pragma mark - UITextFieldDelegate

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];
    return YES;
}


@end

I have a register view controller which looks like this:

//.h
    #import <UIKit/UIKit.h>
    #import "GAViewController.h"
    #import "GAViewController.m"

    @interface GARegisterViewController : GAViewController

    @end

//.m
#import "GARegisterViewController.h"


@interface GARegisterViewController ()<UIActionSheetDelegate, UINavigationControllerDelegate, UIImagePickerControllerDelegate, UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIButton *registerButton;
@property (weak, nonatomic) IBOutlet UITextField *userNameTextField;
@property (weak, nonatomic) IBOutlet UITextField *passwordTextField;
@property (weak, nonatomic) IBOutlet UITextField *firstNameTextField;
@property (weak, nonatomic) IBOutlet UITextField *lastNameTextField;
@property (weak, nonatomic) IBOutlet UITextField *phoneNumberTextField;
@property (weak, nonatomic) IBOutlet UISegmentedControl *genderSegmentedContoller;

@end

@implementation GARegisterViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self makeTextFieldDelegates];
}

- (void)makeTextFieldDelegates{
    [self.userNameTextField setDelegate:self];
    [self.passwordTextField setDelegate:self];
    [self.firstNameTextField setDelegate:self];
    [self.lastNameTextField setDelegate:self];
    [self.phoneNumberTextField setDelegate:self];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Here is the error I receive: enter image description here enter image description here

Does anyone know I can either fix the error above? Or create a parent class correctly with the textFieldShoudlReturn method so that I don't have to include in all my views.

Thanks!

Upvotes: 1

Views: 187

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726489

I am importing .m because it contains the textfieldshouldreturn method, it also imports the .h file

It is importing .m file that causes duplicate symbols. Importing a .m file causes the file from which it is imported to define the same symbols (such as method implementations and functions / variables with external scope) as the .m file being included, causing the duplication.

For the same reason one should never place @implementation blocks into header files.

In order to fix this, make a header for GAViewController, and declare textFieldShouldReturn: inside it. Remove #import "GAViewController.m" from your headers and .m files, replacing with #import "GAViewController.h". This should fix the problem.

Upvotes: 3

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