Objective C Archives

The best solution is to create base classes for UIViewController and UITableViewController and override their init methods. This will allow you to add ViewControllers to the NavigationController programmatically after a rootViewController. If you put this code in the ViewDidLoad method, it will not be called in this case and the next controller will be pushed with a back text.

BaseViewController in Objective C:

#import "BaseViewController.h"

@interface BaseViewController ()

@end

@implementation BaseViewController

- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
 self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
 if (self) {
 self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];
 }
 return self;
}

@end

#import "BaseViewController.h"

@interface BaseViewController ()

@end

@implementation BaseViewController

- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

if (self) {

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];

}

return self;

}

@end

BaseTableViewController:

#import "BaseTableViewController.h"

@interface BaseTableViewController ()

@end

@implementation BaseTableViewController

- (instancetype)initWithStyle:(UITableViewStyle)style
{
 self = [super initWithStyle:style];
 if (self) {
 self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];
 }
 return self;
}

@end

#import "BaseTableViewController.h"

@interface BaseTableViewController ()

@end

@implementation BaseTableViewController

- (instancetype)initWithStyle:(UITableViewStyle)style

{

self = [super initWithStyle:style];

if (self) {

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];

}

return self;

}

@end

To bind some action to the button click one can use just a custom RACSignal. But then you have to add three more things in every case:
1. Disable button, while action is performing;
2. Show, that action is in progress;
3. Disable button, if input is incorrect and button should not be able to be tapped.

Instead, if you use RACCommand, you get all these things in a box.

Let’s say, we want to bind RACCommand verifyPhoneCommand to a button. We can create a command in a lazy property in a ViewModel:

- (RACCommand *)verifyPhoneCommand
{
    if (! _verifyPhoneCommand) {
        _verifyPhoneCommand = [[RACCommand alloc] initWithEnabled:self.phoneValidSignal
                                                      signalBlock:^RACSignal * _Nonnull(id  _Nullable input) {
                                                          return [self verifyPhone];
                                                      }];
    }
    return _verifyPhoneCommand;
}

- (RACCommand *)verifyPhoneCommand

{

if (! _verifyPhoneCommand) {

_verifyPhoneCommand = [[RACCommand alloc] initWithEnabled:self.phoneValidSignal

signalBlock:^RACSignal * _Nonnull(id _Nullable input) {

return [self verifyPhone];

}];

}

return _verifyPhoneCommand;

}

Here phoneValidSignal is this signal, that is formed by observing a phone variable:

- (RACSignal *)phoneValidSignal
{
    if (!_phoneValidSignal) {
        _phoneValidSignal = [RACObserve(self, phone) map:^id(NSString *phone) {
            return @(phone.length > 0);
        }];
    }
    return _phoneValidSignal;
}

- (RACSignal *)phoneValidSignal

{

if (!_phoneValidSignal) {

_phoneValidSignal = [RACObserve(self, phone) map:^id(NSString *phone) {

return @(phone.length > 0);

}];

}

return _phoneValidSignal;

}

We pass a RACSignal verifyPhone to the RACCommand to do a job:

- (RACSignal *)verifyPhone
{
    return [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {

        [[PhoneManager sharedManager]
         requestVerifyPhone:self.phone
         success:^{

             [subscriber sendNext:@(YES)];
             [subscriber sendCompleted];
             
         } failure:^(NSError *error) {
             
             [subscriber sendError:error];
             
         }];
        
        return nil;
    }];
}

- (RACSignal *)verifyPhone

{

return [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber> _Nonnull subscriber) {

[[PhoneManager sharedManager]

requestVerifyPhone:self.phone

success:^{

[subscriber sendNext:@(YES)];

[subscriber sendCompleted];

} failure:^(NSError *error) {

[subscriber sendError:error];

}];

return nil;

}];

}

This is how we bind a RACCommand to a button:

self.smsRequestButton.rac_command = self.viewModel.verifyPhoneCommand;

1	self.smsRequestButton.rac_command = self.viewModel.verifyPhoneCommand;

To track execution of a RACCommand and show an activity indicator we can use executing property:

[self.viewModel.verifyPhoneCommand.executing subscribeNext:^(NSNumber*  _Nullable x) {
        if (x.boolValue) {
            [self.spinnerView startAnimating];
        }
        else {
            [self.spinnerView stopAnimating];
        }
    }];

[self.viewModel.verifyPhoneCommand.executing subscribeNext:^(NSNumber* _Nullable x) {

if (x.boolValue) {

[self.spinnerView startAnimating];

}

else {

[self.spinnerView stopAnimating];

}

}];

If errors happen during RACCommand execution we can process those errors:

[self.viewModel.verifyPhoneCommand.errors subscribeNext:^(NSError * _Nullable error) {
        [ErrorUtil showError:error from:self onRepeat:^{
            
        }];
    }];

[self.viewModel.verifyPhoneCommand.errors subscribeNext:^(NSError * _Nullable error) {

[ErrorUtil showError:error from:self onRepeat:^{

}];

Alwawee

Tag Archives: Objective C

iOS – How to remove “Back” text from the back button

Using RACCommand and creating custom RACSignals in Objective C

iOS Development