Starting point
I have a class, say A, used by an UI view.
A has a delegate that should notify UI view and this one should be write something on screen.
Question
What is the best approach to achieve this feature?
Seems something like observer-observable pattern
Code
---A.h
#interface A : NSObject
#end
---A.m
#implementation A
-(void)fooDelegate:(FooType *)sender {
/* Here I need to notify UI (that change notificationArea.text) */
}
---UIView.h
#interface UIView : UIViewController
#property(strong, nonatomic, retain) A* a;
#property(strong, nonatomic) IBOutlet UITextField *notificationArea;
#end
Based on the comments, I guess just code is what you're looking for...
Create your delegate protocol:
#protocol ADelegate;
#interface A : NSObject
#property (nonatomic, weak) id <ADelegate> delegate;
#end
#protocol ADelegate <NSObject>
#optional
-(void)fooDelegate:(A *)a;
#end
Notify your delegate:
#implementation A
-(void)fooDelegate:(FooType *)sender {
if ([[self delegate] respondsToSelector:#selector(fooDelegate:)]) {
[[self delegate] fooDelegate:self];
}
}
#end
Conform to the delegate protocol:
#import "A.h"
#import "MyView.h"
#interface MyView <ADelegate>
#end
#implementation MyView
-(void)fooDelegate:(A *)a {
// update text field here
}
#end
Finally, whenever you create an instance of A, set the delegate (where self in this example is an instance of MyView:
A *a = [[A alloc] init];
[a setDelegate:self];
Related
I need to pass a string from a NSObject class to a UIViewController, I understand that the best way is delegation but the delegate method isn't being called. I'm trying to set the UILabel an DieFacesViewController as the selectedOption from TemporarySelection.
A tableview shows the value of CustomOptionStore, once it's tapped passes its value to TemporarySelection and opens the modal view DieFacesViewCountroller which should, at least in my mind, take the label value from TemporarySelection. The reason I created TemporarySelection is because the DieFacesViewController will be used by other classes, not only by CustomOptionStore, and it will need to load the label from all those classes when different tableViews are selected.
I tried to set the delegate as self in both viewDidLoad and viewWillAppear with no luck, I don't understand if the view loads before being able to call the delegate method or if there's something wrong the way I set the method up.
I've been stuck here for two days, this is the first time I post a question so please forgive me if it's a bit confused.
my delegator class TemporarySelection.h is
#import <Foundation/Foundation.h>
#import "CustomOptionsStore.h"
#class DieFacesViewController;
#protocol TemporarySelectionDelegate <NSObject>
-(void)sendSelection;
#end
#interface TemporarySelection : NSObject
#property (nonatomic, weak) id <TemporarySelectionDelegate> delegate;
#property (nonatomic, strong) NSString *selectedOption;
-(void)addSelection: (CustomOptionsStore *) selection;
#end
and my TemporarySelection.m is
#import "TemporarySelection.h"
#implementation TemporarySelection
-(void)addSelection: (CustomOptionsStore *) selection{
self.selectedOption = selection.description;
[self.delegate sendSelection];
}
#end
the delegate class DiewFacesViewController.h is
#import <UIKit/UIKit.h>
#import "SelectedStore.h"
#import "TemporarySelection.h"
#interface DieFacesViewController : UIViewController <TemporarySelectionDelegate>
#property (strong, nonatomic) IBOutlet UILabel *SelectionName;
#end
and the DieFacesViewController.m is
#import "DieFacesViewController.h"
#interface DieFacesViewController ()
#end
#implementation DieFacesViewController
- (void)viewDidLoad {
TemporarySelection *ts = [[TemporarySelection alloc]init];
ts.delegate = self;
[super viewDidLoad];
}
-(void)sendSelection{
TemporarySelection *ts = [[TemporarySelection alloc]init];
self.SelectionName.text = ts.selectedOption;
}
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:YES];
}
You are not setting the delegate object properly.Check the above code
#import "DieFacesViewController.h"
#interface DieFacesViewController ()<TemporarySelectionDelegate>
{
//global object
TemporarySelection *ts;
}
#end
#implementation DieFacesViewController
- (void)viewDidLoad {
ts = [[TemporarySelection alloc]init];
ts.delegate = self;
[super viewDidLoad];
}
-(void)sendSelection{
//Use the object to extract
self.SelectionName.text = ts.selectedOption;
}
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:YES];
}
I'm trying to implement delegate method between 2 classes in my app but the delegated method is not called.
Here is my code :
PBPartnersService.h
#protocol PBPartnersServicesDelegate <NSObject>
#required
-(void) didReceiveNewsDatasFromPartners:(NSDictionary *)Datas;
#end
Then I make my #property :
#interface PBPartnersServices : NSObject
#property (nonatomic, weak) id<PBPartnersServicesDelegate> delegate;
#end
In my PBPartnersService.m I call my delegate method (when I print self.delegate I get 'nil') :
if ([self.delegate respondsToSelector:#selector(didReceiveNewsDatasFromPartners:)]) {
[self.delegate didReceiveNewsDatasFromPartners:obj];
}
In my other class PBTicketsService.h I instantiate the first one :
#interface PBTicketsService : NSObject <PBPartnersServicesDelegate>
#property (nonatomic,strong) NSDictionary *ticketList;
#property (nonatomic, strong) PBPartnersServices *partnersServices;
- (void) prepareForDelegate;
#end
I made a method in PBTicketsService.m to set the partnersServices as a delegate :
- (void) prepareForDelegate{
self.partnersServices = [[PBPartnersServices alloc] init];
[self.partnersServices setDelegate:self];
}
and then I have my function who is never call :
-(void) didReceiveNewsDatasFromPartners:(NSDictionary *)Datas{
}
You should use Dependency injection: either add ticketsService as an argument of your partnerServices constructor, or do the opposite.
When you allocate the partnerServices property a second time your partnerServices will save in a new memory-adress. And for this object you didn't set the delegate property.
I have been staring at code too long and know i am doing something silly here with my Protocols if someone could enlighten me that would be great.
Trying to get my areaNameLabel to change to cell.nameLabel.text across viewcontrollers.
FirstTableViewController.h
#import <UIKit/UIKit.h>
#import "FirstTableCell.h"
#import "SecondViewController.h"
#interface FirstTableViewController : UITableViewController <UITableViewDataSource, UITableViewDelegate, passNames>
#property (nonatomic, strong) NSString *passedNameString;
#property (strong, nonatomic) NSMutableArray *names;
FirstTableViewController.m
#import "FirstTableViewController.h"
#interface FirstTableViewController ()
#end
#implementation FirstTableViewController
#synthesize names;
#synthesize passedNameString;
- (void)viewDidLoad
{
[super viewDidLoad];
names = [NSMutableArray arrayWithObjects:#"Bondi", #"Miranda", nil];
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
FirstTableCell *cell = (FirstTableCell *)[tableView cellForRowAtIndexPath:indexPath];
if ([cell.nameLabel.text isEqualToString:#"Bondi"]) {
SecondViewController *mapController = [[SecondViewController alloc] init];
NSString *passedName = cell.nameLabel.text;
mapController.passedNameString = passedName;
[mapController setDelegate:self];
self.tabBarController.selectedIndex = 1;
NSLog(#"Hola");
}
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
#pragma mark - Protocol Methods
-(void)setAreaName:(NSString *)areaName {
passedNameString = areaName;
}
SecondViewController.h
#import <UIKit/UIKit.h>
#protocol passNames <NSObject>
-(void)setAreaName:(NSString *)areaName;
#end
#interface SecondViewController : UIViewController <RMMapViewDelegate>
#property (retain) id <passNames> delegate;
#property (nonatomic, strong) NSString *passedNameString;
#property (weak, nonatomic) IBOutlet RMMapView *mapView;
#property (weak, nonatomic) IBOutlet UILabel *areaNameLabel;
#end
SecondViewController.m
#import "SecondViewController.h"
#import "FirstTableViewController.h"
#interface SecondViewController ()
#end
#implementation SecondViewController #synthesize areaNameLabel; #synthesize delegate, passedNameString;
- (void)viewDidLoad {
[super viewDidLoad];
passedNameString = areaNameLabel.text;
[[self delegate] setAreaName:passedNameString];
if ([areaNameLabel.text isEqualToString:#"Bondi"]) {
NSLog(#"You got it!");
}
}
Any other critiques feel free to throw in - I've had a look at some other Protocol questions and examples but i know it is something obvious i am missing.
The problem is that your SecondViewController has no relationship to the passNames protocol (being declared in the same header does not count).
Since protocol methods need to be implemented (or their implementation be inherited from the base) and your SecondViewController does not do that, you cannot call setAreaName: without triggering an error.
If you would like to use a common protocol in two view controllers, you need to do this:
Give passNames protocol a more conventional name that starts in a capital letter, and put it in a separate header file
Include that header in both view controllers (the #import "SecondViewController.h" in the FirstTableViewController.h does not look right)
Put implementations of setAreaName: in both view controllers.
Note that you cannot put the common functionality in a superclass, because your view controllers inherit from different bases (i.e. UIViewController and UITableViewController).
I have this delegate that is not working out as planned, I have it setup like so. I want to call the function NSLog(show); I am not too sure why this isn't work, but works with my other viewcontroller. I must be missing some small detail.
AccountViewController.h
#protocol AccountViewControllerDelegate;
#interface AccountViewController : UIViewController{
}
#property (nonatomic, assign) id <AccountViewControllerDelegate> accountViewDelegate;
#end
#protocol AccountViewControllerDelegate <NSObject>
- (void)showLabel;
#end
AccountViewController.m
-(IBAction)save:(id)sender {
[self showLabel];
}
- (void)showLabel {
if (self.accountViewDelegate) {
NSLog(#"showlabel");
[self.accountViewDelegate showLabel];
}
}
MapViewController.m
-(void)showLabel {
NSLog(#"SHOW");
}
you haven't shown where you assign the MapViewController to be the delegate of the AccountViewController. Perhaps thats what you are missing
//(from somewhere in the MapViewController)
AccountViewController *accountVC = //however you instantiate it (segue, storyboard etc
accountVC.accountViewDelegate = self;
Kindly note that delegate should not have strong reference.
So use
#property (unsafe_unretained) id <AccountViewControllerDelegate> accountViewDelegate;
Now in MapViewController.m or MapViewController.h conform to this protocol as
#interface MapViewController : UIViewController <AccountViewControllerDelegate>{
}
Then in MapViewController.m please do
AccountViewController *accountVC = [[AccountViewController alloc]init]; // initialize it with whatever be like storyboard or nib
accountVC.accountViewDelegate = self;
Your AccountViewController.h file should look like this
#protocol AccountViewControllerDelegate <NSObject>
- (void)showLabel;
#end
#interface AccountViewController : UIViewController{
}
#property (unsafe_unretained) id <AccountViewControllerDelegate> accountViewDelegate;
#end
Here what you should have in your different files:
AccountViewController.h
Note that "assign" is mainly for primitives like NSInteger, CGFloat, BOOL (that is, for properties that are not objects). Use "weak" to keep a pointer toward your delegate without incrementing his retain count.
#protocol AccountViewControllerDelegate;
#interface AccountViewController : UIViewController
#property (nonatomic, weak) id <AccountViewControllerDelegate> accountViewDelegate;
#end
#protocol AccountViewControllerDelegate <NSObject>
- (void)showLabel;
#end
AccountViewController.m
Here, it is usually good practice to check if the delegate isn't nil and if it has the method you want to call implemented. Use respondToSelector for that.
-(IBAction)save:(id)sender {
[self showLabel];
}
- (void)showLabel {
if (self.accountViewDelegate && [self.accountViewDelegate respondsToSelector:#selector(showLabel)]) {
NSLog(#"showlabel");
[self.accountViewDelegate showLabel];
}
}
MapViewController.h
Be sure to import "AccountViewController.h" here.
#import "AccountViewController.h"
#interface MapViewController : UIViewController <AccountViewControllerDelegate>
#end
MapViewController.m
Put the following where you were instantiating your AccountViewController object:
//Somewhere
AccountViewController *accountViewController = [[AccountViewController alloc] init];
accountViewController.accountViewDelegate = self;
and this is your delegate's method implementation:
- (void)showLabel {
NSLog(#"SHOW");
}
I've a main class where I want to define two protocols (1 used by a class A, the other by class B) (ios 6.1, xcode 4.6.3 , ARK mode, storyboard project).
According to official syntax, all my code seems to be correct.
But when I try to use the second delegate , nothing work correctly, my 2nd delegate does not respond
**HEADER myProtocols.h**
#import ...
#class myProtocols;
#protocol myProtocol1 <NSObject>
// list of methods and properties
doStuff:(float) myValue;
#end
#protocol myProtocol2 <NSObject>
// list of methods and properties
doOtherStuff:(float) myValue2 andText:(NSString *)myText andType:(NSString *)myType;
#end
#interface myProtocols:NSObject
{
__unsafe_unretained id <myProtocol1> _myDelegate1;
__unsafe_unretained id <myProtocol2> _myDelegate2;
}
#property (nonatomic, assign) id <myProtocol1> myDelegate1;
#property (nonatomic, assign) id <myProtocol2> myDelegate2;
#end
**MESSAGES myProtocols.m**
#import myProtocols.h
#implementation myProtocols
#synthesize myDelegate1 = _myDelegate1
#synthesize myDelegate2 = _myDelegate2
...
if ([_myDelegate1 respondsToSelector:#selector(doStuff:)])
[_myDelegate1 doStuff:3.5]; **// THIS DELEGATE WORK VERY WELL**
...
if ([_myDelegate2 respondsToSelector:#selector(doOtherStuff:andText:andType:)])
[_myDelegate2 doOtherStuff:4.5 andText:#"YES MAN" andType:#"YES BRO"];
**// THIS DELEGATE DONT WORK, IT'S LIKE IT DOESNT INIT**
...
#end
**HEADER classA.h**
#import "myProtocols.h"
#interface classA: UIViewController <myProtocol1>
#property(strong, nonatomic) myProtocols *myProtoVC;
//-(void) doStuff:(float) myValue; according to comments, nothing to do :(
#end
**MESSAGES classA.m**
#import "classA.h"
#interface classA ()
#end
#implementation classA
- (void)viewDidLoad
{
[super viewDidLoad];
_myProtoVC = [[myProtocols alloc] init];
_myProtoVC.myDelegate1 = self;
}
-(void) doStuff:(float) myValue
{
NSLog(#" YES VALUE IS %f",myValue);
}
**HEADER classB.h**
#import "myProtocols.h"
#interface classB: UIViewController <myProtocol2>
#property(strong, nonatomic) myProtocols *myProtoVC;
//-(void) doOtherStuff:(float) myValue2 andText:(NSString *)myText andType:(NSString *)myType; according to comments, nothing to do :(
#end
**MESSAGES classB.m**
#import "classB.h"
#interface classB ()
#end
#implementation classB
- (void)viewDidLoad
{
[super viewDidLoad];
_myProtoVC = [[myProtocols alloc] init];
_myProtoVC.myDelegate2 = self;
}
-(void) doOtherStuff:(float) myValue2 andText:(NSString *)myText andType:(NSString *)myType;
{
NSLog(#" YES VALUE IS %f and text %# and type %#",myValue2,myText,myType);
}
So, my mistake is to call [_myDelegate2 doOtherStuff..] directly inside a function in myProtocols called only by classA.
Then, if I want to call a function in myProtocols using both delegate I MUST init both these delegates in the class (A or B doesnt matter) I use to call this function:
**MESSAGES myProtocols.m**
#import myProtocols.h
#implementation myProtocols
#synthesize myDelegate1 = _myDelegate1
#synthesize myDelegate2 = _myDelegate2
-(void) pleaseDoIt
{
if ([_myDelegate1 respondsToSelector:#selector(doStuff:)])
[_myDelegate1 doStuff:3.5]; **// THIS DELEGATE WORK VERY WELL**
...
if ([_myDelegate2 respondsToSelector:#selector(doOtherStuff:andText:andType:)])
[_myDelegate2 doOtherStuff:4.5 andText:#"YES MAN" andType:#"YES BRO"];
**// THIS DELEGATE NOW WORK VERY WELL**
}
#end
**HEADER classA.h**
#import "myProtocols.h"
#import "classB.h"
#interface classA: UIViewController <myProtocol1>
#property(strong, nonatomic) myProtocols *myProtoVC;
#property(strong, nonatomic) classB *classBVC;
//-(void) doStuff:(float) myValue;
#end
**MESSAGES classA.m**
#import "classA.h"
#interface classA ()
#end
#implementation classA
- (void)viewDidLoad
{
[super viewDidLoad];
_myProtoVC = [[myProtocols alloc] init];
_classBVC = [[myProtocols alloc] init];
_myProtoVC.myDelegate1 = self;
_myProtoVC.myDelegate2 = _classBVC // THIS IS THE POINT!!!
[_myProtoVC pleaseDoIt];
}
-(void) doStuff:(float) myValue
{
NSLog(#" YES VALUE IS %f",myValue);
}