I use this code, but "it works" doesn't happen.
DetailViewController.h
[#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#protocol ProtocolNameDelegate
-(void)DoSomething;
#end
#interface DetailViewController : UIViewController {
id<ProtocolNameDelegate> _delegate;
}
#property (strong, nonatomic) id<ProtocolNameDelegate> _delegate;
DetailViewController.m
#synthesize _delegate;
- (void)viewDidLoad
{
[super viewDidLoad];
[_delegate DoSomething];
}
MasterViewController.h
#interface MasterViewController : UITableViewController <ProtocolNameDelegate>
MasterViewController.m
-(void)DoSomething
{
NSLog(#"It works");
}
I think i have to add something like:
MasterViewController* mvc = [[MasterViewController alloc] init];
mvc._delegate = self;
But it gives an error, and by the way will it create another instance of MasterViewController?
Instead of
MasterViewController* mvc = [[MasterViewController alloc] init];
mvc._delegate = self;
write this,
DetailViewController* svc = [[DetailViewController alloc] init];
dvc._delegate = self;
You made mistake in implementation.
Abstract of implementation should be.
Create Protocol in DetailVC.
Create Property for Delegate, Synthesize, and make call.
Import DetailVC in MasterVC and include delegate in MasterVC.h
Implement protocol method in MasterVC.m
Create instance of DetailVC and assign DetailVCObj.delegate = self;
In MasterViewController.m, you need to allocate and intialise DetailViewController somewhere
DetailViewController* dvc = [[DetailViewControlleralloc] init];
dvc._delegate = self;
Also, because you have written [_delegate doSomething] in
DetailviewController's viewDidLoad method,
it means you must set dvc._delegate = self; in MasterViewController.m
before loading dvc's view (before addSubview or anything that loads view).
Related
Through delegation I created a view controller that takes the input from textfields and passes it back and adds it to an nsmutablearray, successfully adding a row for it. whenever i navigate away from the tableview my newly appended object just disappears. Here is some code to give you a better idea of what i might be doing wrong.
TableViewController.h -
#interface TableViewController : UITableViewController<UITableViewDelegate, UITableViewDataSource>
#property(strong,nonatomic)NSMutableArray *codeList;
#property(strong,nonatomic)NSMutableArray *codeArray;
#end
TableViewController.m -
#interface TableViewController ()
#end
#implementation MCTableViewController
#synthesize codeList;
#synthesize codeArray;
- (void)viewDidLoad {
[super viewDidLoad];
self.tableView.delegate = self;
self.tableView.dataSource = self;
self.codeList = [NSMutableArray arrayWithObjects:#"Array",
#"Pointer",
#"Class",
#"Protocol",
#"Delegate",
nil];
self.codeDescArray = [NSMutableArray arrayWithObjects:
#"Array Description",
#"Pointer Description",
#"Class Description",
#"Protocol Description",
#"Delegate Description",
nil];
)
In the same class I programmatically created a button that moves to the view where data is supposed to be passed back. code below. This is done through delegation.
- (void)addNewCodeButtonPressed {
AddNewCodeVC *addVC = [[AddNewCodeVC alloc] init];
addVC.dataDelegate = self;
UINavigationController *navBar = [[UINavigationController alloc]initWithRootViewController:addVC];
[self.navigationController presentViewController:navBar animated:YES completion:nil];
}
Here is where the delegate logic is created in AddNewCodeVC.h -
#import <UIKit/UIKit.h>
#import "TableViewController.h"
#class AddNewCodeVC;
#protocol addNewCellData <NSObject>
- (void)sendDataToTableView:(NSString*)code codeDesc: (NSString*)desc;
#end
#interface AddNewCodeVC : UIViewController<UITextFieldDelegate> {
__weak id dataDelegate;
}
#property(weak,nonatomic)id<addNewCellData>dataDelegate;
#property(strong,nonatomic)UITextField *codeTextfield;
#property(strong,nonatomic)UITextField *descTextfield;
#end
finally here is the AddNewCodeVC.m -
#import "AddNewCodeVC.h"
#interface AddNewCodeVC ()
#end
#implementation AddNewCodeVC
#synthesize dataDelegate;
- (void)viewDidLoad {
[super viewDidLoad];
self.codeTextfield.delegate = self;
self.descTextfield.delegate = self;
//Programmatically created both textfields, nothing special
}
//"saveNewCode" is action for another button i created
- (void)saveNewCode {
sendDataToTableView:self.codeTextfield.text codeDesc:self.descTextfield.text];
[self.dataDelegate sendDataToTableView:self.codeTextfield.text codeDesc:self.descTextfield.text];
NSLog(#"CODE: %#", self.codeTextfield.text);
NSLog(#"DESC: %#", self.descTextfield.text);
[self dismissViewControllerAnimated:YES completion:nil];
}
The code works but nsmutable array wont hold the passed values if i navigate away from the TableViewController. I think this is because my main view controller programmatically segues to the tableview controller and creates a new instance of it, so that might have some effect? I'll leave some code below just in case it is relevant.
MainviewController.m -
- (void) tableViewBtnPressed:(UIBarButtonItem *)sender {
TableViewController *tableVC = [[TableViewController alloc] init];
//This for another delegate I created, not relevant
tableVC.selectedDataDelegate = self;
UINavigationController *navBar = [[UINavigationController alloc]initWithRootViewController:tableVC];
[self.navigationController presentViewController:navBar animated:YES completion:nil];
}
Hopefully this code is enough to illustrate the problem, i hope someone has an idea whats going on with the NSMutableArray, and why it isn't holding any new objects that are passed into it, any help is appreciated.
AddBillViewController.h:
#protocol AddBillDelegate <NSObject>
- (void)addBillViewControllerDidAddOneBill;
#end
#interface AddBillViewController : UIViewController
#property (retain, nonatomic)id <AddBillDelegate> delegate;
#end
AddBillViewController.m:
- (IBAction)AddBill:(id)sender {
[self.delegate addBillViewControllerDidAddOneBill];
[self dismissViewControllerAnimated:YES completion:nil];
}
HomeViewController.m:
#interface HomeViewController () <AddBillDelegate>
#property (strong, nonatomic)AddBillViewController *abVC;
#end
#implementation HomeViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.abVC = [[AddBillViewController alloc] init];
self.abVC.delegate = self;
}
- (void)addBillViewControllerDidAddOneBill {
NSLog(#"Added a bill.");
}
#end
As you can see, there is button in AddBillViewController, when the button is pressed, addBill method will be called, then the delegate method addBillViewControllerDidAddOneBill in HomeViewController should be called, however in fact, it doesn't.
I think you are not getting the reference right here in this line
self.abVC = [[AddBillViewController alloc] init];
If you are performing a segue, like the AddBillViewController is your next controller, set delegate in performSegue: function
like
AddBillViewController *vc = [segue destinationViewController];
[vc setDelegate:self];
I'm having the following problem.
I've created a custom view controller that has a some useful methods that I need.
This is the code in the .h
#interface MYViewController : UIViewController
- (void)method;
- (void)otherMethod;
#end
This is my init method of MYViewController class:
- (instancetype)init
{
self = [super init];
return self;
}
Then when I try to extend that class I can't set the title of the child controller. For example, in "MYOtherController.h"
#interface MYOtherViewController : MYViewController
- (void)childControllerMethod;
#end
And this is the init of MYOtherViewController:
- (instancetype)init
{
self = [super init];
return self;
}
And then, if I instantiate a MYOtherViewController object and try to set the title, it happens nothing. For example:
MYOtherViewController *controller = [[MYOtherViewController] alloc] init];
controller.title = #"Hello";
If I put this in the viewDidLoad of the MYOtherViewController class it logs that title is nil:
- (void)viewDidLoad {
NSLog(#"title: %#", self.title);
[super viewDidLoad];
}
Why can't set the title in this child class?
the title for the viewcontroller hasnt been made yet after the alloc init, you would need to set it after the viewDidLoad (which is when all the UI elements have been initialized), so what you can do is make an #property on the viewcontroller which you set after the alloc init, then in the viewDidLoad, set the title to the value of the #property
I'm using a Split View Controller for an iPad app. I'm trying to send a label change to the detailReceiving Controller from the rootSending Controll when a button is pushed. I've read through tutorials on protocols and came up with the code below. When I click the button on rootSending, nothing happens to the label on detailReceiving. Do I have to do something else with a splitViewContoller so that the label will update? Shouldn't detailReceiving change the label when it receives the message?
rootSending.h
#import <UIKit/UIKit.h>
#protocol TestDelegate <NSObject>
-(void)tester:(NSString*)testString;
#end
#interface rootSending : UIViewController
#property (nonatomic, assign) id <TestDelegate> delegate;
#end
rootSending.m
#import "rootSending.h"
#implementation rootSending
#synthesize delegate;
-(void)viewDidLoad{
}
-(IBAction)buttonPressed:(id)sender{
[delegate tester:#"button pressed"];
}
#end
detailReceiving.m
#import "detailReceiving.h"
#import "rootSending.h"
#interface detailReceiving ()<TestDelegate>{
IBOutlet UILabel *label2;
}
#end
#implementation detailReceiving
-(void)viewDidLoad{
rootSending *obj = [rootSending alloc];
obj.delegate = self ;
}
-(void)tester:(NSString *)testString{
label2.text = testString;
}
#end
First of all, never ever have an alloc without an init! But in this case, even if you did use alloc/init, it still wouldn't work because that just creates a new instance of rootSending, not the one that you have in your split view. You need to get a reference to the one you have, which you can get from the split view controller,
-(void)viewDidLoad{
rootSending *obj = (rootSending *)self.splitViewController.viewControllers.firstObject;
obj.delegate = self;
}
After Edit:
If your mate controller is embedded in a navigation controller, then you need to get the navigation controller's topViewController to get your reference.
-(void)viewDidLoad{
UINavigationController *nav = (UINavigationController *)self.splitViewController.viewControllers.firstObject;
xmlListOfItems *obj = (xmlListOfItems *)nav.topViewController;
obj.delegate = self;
}
I have been searching all morning how to do this. I have 2 View Controllers. From the root View Controller (ViewControllerA - which is a table view controller) you can go push to the second view controller (ViewControllerB).
In the ViewControllerB, there are two fields: contacts & textBody. When the user is done they can click on "Add". This will then go back to ViewControllerA. What I am trying to do now, is for every time that process occurs, all the information from ViewControllerB the user just added goes into a cell in ViewControllerA. The user can then add as many cells as they like.
What I can't do however, is get the information across the view controllers. I have been looking all morning at using the app delegate, singletons??, protocols, sharing properties, etc! But I am still stuck.
What I want to do, but can't, is for every time the user clicks "Add" on ViewControllerB, contacts & texts are put into an array. This array is then put into another array which holds all the smaller arrays which the user has created? If you have an ideas, or links to similar/sample code or tutorials, that would be much appreciated!
Try this using the delegate method as follows
Download Sample Project with XIBs
Download Sample Project With Storyboard
ParentViewController.h
#import <UIKit/UIKit.h>
#interface ParentViewController : UIViewController {
NSMutableArray *dataArray;
}
- (void)passData:(NSMutableArray *)array;
#end
ParentViewController.m
#import "ParentViewController.h"
#import "ChildViewController.h"
#implementation ParentViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Initialise the mutable array.
dataArray = [[NSMutableArray alloc] init];
}
- (IBAction)btnGoToSecondView:(id)sender {
ChildViewController *secondVC = [[ChildViewController alloc] initWithNibName:#"ChildViewController" bundle:nil];
secondVC.delegate = self;
[self presentViewController:secondVC animated:YES completion:nil];
}
- (void)passData:(NSMutableArray *)array {
[dataArray addObject:array];
NSLog(#"Data Passed = %#",dataArray);
}
#end
ChildViewController.h
#import <UIKit/UIKit.h>
#import "ParentViewController.h"
#class ParentViewController;
#interface ChildViewController : UIViewController {
NSMutableArray *tempArray;
}
#property (strong, nonatomic) IBOutlet UITextField *txtContact;
#property (strong, nonatomic) IBOutlet UITextField *txtTextBody;
#property(nonatomic, assign) ParentViewController *delegate;
#end
ChildViewController.m
#implementation ChildViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Initialise the mutable array.
tempArray = [[NSMutableArray alloc] init];
}
- (IBAction)btnPassDataBack:(id)sender {
if([self.delegate respondsToSelector:#selector(passData:)]) {
[tempArray addObject:_txtContact.text];
[tempArray addObject:_txtTextBody.text];
[self.delegate passData:tempArray];
}
[self dismissViewControllerAnimated:YES completion:nil];
}
- (void)viewDidUnload {
[self setTxtContact:nil];
[self setTxtTextBody:nil];
[super viewDidUnload];
}
#end
With Storyboard
If you are using storyboard then create a ParentViewController segue ChildViewController and give it a identifier in my sample it showChildView
Then use the following code to set the delegate
// Calling the segue to go to the child view and setting up the delegate.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"showChildView"]) {
ChildViewController *childVC = segue.destinationViewController;
childVC.delegate = self;
}
}
Then to dismiss back to the ParentViewController use the following code (from my sample)
- (IBAction)btnPassDataBack:(id)sender {
if([self.delegate respondsToSelector:#selector(passData:)]) {
[tempArray addObject:_txtContact.text];
[tempArray addObject:_txtTextBody.text];
[self.delegate passData:tempArray];
}
[self.navigationController popToRootViewControllerAnimated:YES];
}
I would recommend using a singleton instance of your NSMutableDictionary as they have bailed me out of your exact situation multiple times (including custom frameworks and UITabBarControllers). Here is an example I'm currently using to implement a singleton. This methodology is also ARC-safe as well
mySingleton.h
#import <Foundation/Foundation.h>
#interface mySingleton : NSObject {
}
+ (NSMutableDictionary *) myMutableDict;
#end
mySingleton.m
#import "mySingleton.h"
#implementation mySingleton
+ (NSMutableDictionary *)myMutableDict
{
static NSMutableDictionary *singletonInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
singletonInstance = [[NSMutableDictionary alloc]init];
});
return singletonInstance;
}
#end
As long as you include mySingleton.h in all of your view controllers you can access the data via [mySingleton myMutableDict]. For example: [[mySingleton myMutableDict] setObject:myObject forKey:myKey];
Good luck!
If the information is really "global" - it has only one instance across the whole app - then you should create a singleton as DB80Buckeye suggested.
If the information is something that truly belongs to ViewController1 and you want it to be modified in ViewController2 (ie ViewController2 is really part of ViewController1, it just happens to be on another screen), then you should pass that as part of the constructor of ViewController2.
-(void)view_controller_1_that_push_view_controller_2_onto_the_stack {
ViewController2* vc2 = [[ViewController2 alloc] initWithInformation:your_information];
[self.navigationController pushViewController:vc2 animated:YES];
}
#interface ViewController2
-(id)initWithInformation:(YourInformationClass*)info;
#end
Another way is to use notifications.
There are two ways to go here. The standard pattern for doing this is delegation. You don't need a singleton. ViewControllerA manages and lists your data. ViewControllerB doesn't need to know anything about all of that data so there's no reason to expose it via a singleton, etc.
Create a delegate protocol in ViewControllerB's header file. Something like this:
#protocol ViewControllerBDelegate
- (void)addContact:(NSString *)contact withBody:(NSString *)textBody;
#end
Now, specify that ViewControllerA will implement the delegate protocol in its header:
#interface ViewControllerA : UIViewController <ViewControllerBDelegate>
Don't forget to import ViewControllerB.h at the top of ViewControllerA's header.
In ViewControllerA's implementation, implement the delegate method you specified in the protocol:
- (void)addContact:(NSString *)contact withBody:(NSString *)textBody {
[self.someArray addObject:[[SomeObject alloc] initWithContact:contact body:textBody]];
[self.tableView reloadData];
}
That's obviously just an example -- not sure how you're managing your data structure and it's probably better to insert the cell someplace that makes sense.
Declare a delegate reference in ViewControllerB's header:
#property (weak, nonatomic) id<ViewControllerBDelegate> delegate;
When you present ViewControllerB, set ViewControllerA as the delegate.
ViewControllerB *b = [[ViewControllerB alloc] init...];
b.delegate = self;
In the selector triggered by the add button in ViewControllerB, call back on the delegate before popping the view controller off the navigation stack:
[self.delegate addContact:contact withBody:text];
where contact and text are the values the user entered.
One could also use a block instead of a delegate but the principle is the same -- have the second view controller only be responsible for taking input, in your case, and pass it back to the view controller managing the data.
Alternatively for delegate suggest using the following:
ViewControllerA.h:
#property (nonatomic, strong) ViewControllerB* viewControllerB;
In ViewControllerA.m
if (!self.viewControllerB)
{
self.viewControllerB = [[ViewControllerB alloc] initWithNibName: #"ViewControllerBr" bundle: nil];
}
[self.navigationController pushViewController: self.viewControllerB
animated: YES];
...
- (void) viewWillAppear: (BOOL) animated
if (self.viewControllerB)
{
NSString* contact = self.viewControllerB.contact;
NSLog(#"%#", contact);
}
...