I have custom UIButton which programmatically interacts (triggers) with ViewController methods via protocol. But the behaviour of the button has to be dependent on the ViewController placed on. I do this to minimise amount of code in ViewControllers itself, as the button has to remain the same and bear the same functions (navigation).
Is there any way in UIButton's custom class to get the ViewController it is placed on?
I'd follow #rmaddy advice in a specific way, borrowing from the SDK's style
// MyCutomButton.h
#protocol MyCustomButtonDatasource;
#interface MyCustomButton : UIButton
#property(weak,nonatomic) IBOutlet id<MyCustomButtonDatasource>datasource;
// etc
#end
#protocol MyCustomButtonDatasource <NSObject>
#optional
- (NSString *)howShouldIBehave:(MyCustomButton *)button;
#end
Now the button can have it's datasource set in IB. View controllers that include it will need a little additional code (sorry, it's unavoidable in a good design). They will declare themselves as implementing MyCustomButtonDatasource.
When MyCustomButton needs to behave conditionally based on where it's placed, it can ask its datasource...
// MyCustomButton.m
NSString *string = #"defaultBehavior"; // per #RichardTopchiy's suggestion
if ([self.datasource respondsToSelector:#selector(howShouldIBehave:)])
string = [self.datasource howShouldIBehave:self];
// string is just made-up here, have it answer something simple (int, BOOL)
// that lets the button proceed with the right behavior. Don't ask for
// anything that relies on specific knowledge of how MyCustomButton
// is implemented
EDIT - To create the relationship, if you've decorated the property as an IBOutlet (as shown above), you should be able to setup the relationship in IB. Declare your view controller as implementing <MyCustomButtonDatasource>. Select your custom button, then the connections inspector, then drag to your view controller.
Alternatively, make the button itself an IBOutlet property in the view controller and, in viewDidLoad, do:
self.customButton.datasource = self;
The last way to do it is give your button a tag, say, 128, then:
MyCustomButton *customButton = (MyCustomButton *)[self.view viewWithTag:128];
self.customButton.datasource = self;
Related
I am trying to do the following, and not able to find a straightforward answer.. It is related to this :Passing uitextfield from one view to another. But not exactly.
I have a Firstview.m, from which I push to a Secondview.m. The Secondview.m has a UITextView. I allow the user to edit the UITextView on Secondview.m. Now I want to store this text value in a variable in Firstview.m. One way to to do this is as follows
in Firstview.h
#property (nonatomic) Secondview *secondView;
That is keep a secondView variable in Firstview itself. But this doesn't seem efficient. Ideally I should only have 1 NSString text field in FirstView. What is the right way to do this ? Thanks
You can achieve this by using Delegation in Objective-C.
In your SecondView.h add following right after Header Inclusion
#protocol YourDelegateName <NSObject>
-(void)setText:(NSString *)strData;
#end
Also add delegate property to your header for accessing them in calling class, like below (This goes with other properties declaration in SecondView.h file):
#property (nonatomic, weak) id<YourDelegateName> delegate;
Now, Comes the calling the delegate part. Say, you want to save the text value of UITextView of SeconView in strTextViewData of FirstView class, when the following event occurs:
- (IBAction)save:(id)sender
{
[self.delegate setText:self.txtView.text]; // Assuming txtView is name for UITextView object
}
Now, In FirstView.h add YourDelegateName in delegate list like below:
#interface FisrtView : ViewController <YourDelegateName>
#property (nonatomic, reatin) NSString *strTextViewData;
#end
And then in FisrtView.m file when you create instance of SecondView class, set delegate to self like below:
SecondView *obj = [[SecondView alloc] initWithNibName:#"SeconView" bundle:nil];
obj.delegate = self; // THIS IS THE IMPORTANT PART. DON'T MISS THIS.
Now, Implement the delegate method:
-(void)setText:(NSString *)strData
{
self.strTextViewData = strData;
}
Applying this to your code will do what you want. Also, Delegation is one of the most important feature of Objective-C language, which - by doing this - you will get to learn.
Let me know, if you face any issue with this implementation.
Newbie question for Xcode gurus...
I have two views. They both use the same custom class. In view_1 I have a button and when this is pressed view_2 will show. In view_2 I have a label which will have it´s text changed when I press the button in view_1. As of now the Label_1 is nil when I set a breakpoint at it and therefor useless. How can I get to update this label when I press the button? Her are some snippets from my code...
This is my .h file:
#interface ViewController : UIViewController
{
IBOutlet UIButton *buttonSelectTimeInterval;
IBOutlet UILabel *labelTimer;
}
#end
This is the button action in my .m file:
- (IBAction)startPouring_ButtonClick:(id)sender
{
labelTimer.text = #"foo";
}
…but my .m file doesn't seem to know the labelTimer since it is a ´nil´. Why is this so? It is instantiated in the .h file.
Anyone?
You can use NSNotificationCenter. Put this in you IBAction.
[[NSNotificationCenter defaultCenter] postNotificationName:#"buttonPressed" object:nil];
And this to your viewDidLoad.
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(selectorhere) name:#"buttonPressed" object:nil];
somewhere in your .m
(void)selectorhere {
labelTimer.text = #"foo";
}
You can use NSNotificationCenter for this.
Here are the apple documentation link.
First, nothing is "instantiated" in the .h file - that's just the public listing of what properties and methods are available to other classes. Think of the header file as a table of contents, but only for the things the class wants others to see.
Those properties don't exist in memory until the instance of the class itself is created, and then only if you set them to some initial value once they're needed.
How & where are you creating the 2nd view? Is it a storyboard segue or something? The 1st view doesn't seem to have any way of knowing the 2nd one exists, so it won't be able to see or access the label.
View1Class.m
#import View2Class.h
#implementation View1Class
- (IBAction)startPouring_ButtonClick:(id)sender {
//Instantiate the 2ndView when you need it.
// This gives View1 a reference to View2 and its public UILabel.
View2Class * my2ndView = [[View2Class alloc] init];
my2ndView.labelTimer.text = #"foo";
}
#end
As I said, it's still not clear how/where you're actually displaying the 2nd view though, so the snippet above is incomplete. You could use a modal w/a delegate, or this is where NSNotificationCenter is a helpful option - the 2nd view can sign up to get notifications & change accordingly. There are numerous tutorials about creating a 2nd/modal view and displaying it on a button click - you should probably look at those to clarify how the structure of such an app ought to work.
This answer should get you on the right track.
Other specific issues:
Why is the label nil? Because there isn't one...
In this IBAction, which seems to be in View 1:
- (IBAction)startPouring_ButtonClick:(id)sender
{
labelTimer.text = #"foo"; //this is looking for labelTimer in the clicked view.
}
... it is looking for its own labelTimer IBOutlet (in which case it should probably be self.labelTimer.text), and not that of the 2nd view. If the 1st view doesn't even have a UILabel IBOutlet, this is another problem.
If the views have different functions & different properties, they probably shouldn't be instances of the same custom class. If the 1st view doesn't have or need a UILabel, it shouldn't have one in its .h. If the 2nd view doesn't have or need a button it shouldn't have one in its .h. If the views serve different purposes, then make them different classes.
BTW,
Since you're using instance variables for your IBOutlets, you'd need to write your own getter & setter methods if you want to change their values. Did you? To make those values accessible to other classes, you'd need to make those methods public & put them in the .h. It's not good practice for an instance to set its instance variables directly w/o a getter/setter, and other objects definitely should not.
The preferred method is to use #properties for your IBOutlets instead of declaring them as instance variables. This will automatically create the getter & setter methods, backing store in memory, and as of XCode 4.4 it automatically adds #synthesize so you no longer need to do so. Declaring your IBOutlets as "weak" references prevents retain cycles & memory leak, where the view holds on to the outlets & the outlets hold on to the view & nothing ever goes away...
View1Class.h
#interface ViewController : UIViewController
#property (nonatomic, weak) IBOutlet UIButton *buttonSelectTimeInterval;
#end
View2Class.h
#interface ViewController : UIViewController
#property (nonatomic, weak) IBOutlet UILabel *labelTimer;
#end
I am struggling to make a simple thing (at least I think it's simple) but I just can't do it!
I will try to explain a little bit.
It's an app which displays information. When the user is inside a view, he can click on a button, which displays a popoverview, where he can choose which information he wants to know.
Actually, I can't create an action that changes the UILabel text I created in the main view when the user clicks on the popoverview's buttons.
Anyone has any idea?
Just for you to know: the main view I created a class for it, and also for the popoverview. Although, the popover view I created its design in a XIB file (I don't know if this is important, that's why I am putting this).
Well, I hope you guys were able to understand my question.
Thanks in advance.
Fernando.
Just create a property from the viewcontroller and access it from the consumer (other viewcontroller )
You will have to use delegation in order to see changes in the main view when you are making different actions inside the popover. First, you need to create a protocol inside your popover controller header file:
#import <Foundation/Foundation.h>
#class MyPopoverController;
#protocol MyPopoverDelegate
- (void)valueChanged:(NSString*) newVal;
#end
#interface MyPopoverController: UIPopoverController
#property (weak) id<MyPopoverDelegate> delegate;
#end
Then in .m you implement it like this:
- (void) someActionOccured
{
if([self.delegate respondsToSelector:#selector(valueChanged:)]){
[self.delegate valueChanged:valueYouWantToSendBack];
}
}
Remember that in your main class you have to implement MyPopoverDelegate protocol:
#interface MainViewController: UIViewController <MyPopoverDelegate>
And when you instantiate your popover controller:
/*
** inside MainViewController.m
*/
// remember to assign it's delegate
MyPopoverController *popoverController = [MyPopoverController alloc] init];
popoverController.delegate = self;
Also, you'll have to implement the protocol's method:
/*
** inside MainViewController.m
*/
- (void)valueChanged:(NSString*) newVal
{
// process the string and display it where you need it
}
Can someone provide some examples and formal patterns for one-to-one event transfer between UIViewControllers? I think NSNotificationCenter is not applicable for this use case because it is based on event bus and broadcasting patterns for broad state changes and that's why should be used for one-to-many transfers. I know that KVO is not applicable in this case at all too, because it is usually used for communication between model and controller layers in classical MVC realm. So now I know only one way for one-to-one event transfers: delegate pattern. But may be there are even more elegant and simple not easy solutions.
For example:
In the view the action is sent to:
#protocol MapViewDelegate <NSObject>
#required
-(void)MapImageButtonClicked:(UIButton*)sender;
#end
#interface MapView : UIView
{
UIButton *mapButton;
id mapViewDelegate;
}
#property(nonatomic,retain) id mapViewDelegate;
#property(nonatomic,retain) UIButton *mapButton;
.m
[mapButton addTarget:self.delegate action:#selector(mapImageButtonClicked:) forControlEvents:UIControlEventTouchUpInside];
In the view the action will be sent from:
#import "MapView.h"
#interface MapViewController : UIViewController<MapViewDelegate>
{
}
.m
MapView *map = [[MapView alloc] init];
map.delegate = self;
-(void)MapImageButtonClicked:(UIButton*)sender
{
//implement the necessary functionality here
}
Hope you get the idea. Please implement it according to your situation.
You can put that method in a protocol in your view's interface:
#protocol MyViewWithButtonDelegateProtocol<NSObject>
-(void)myButtonAction:(id)sender; #end
you put a new property of NSObject or UIView type called delegate in your view
that has the button.
you make your view that has to handle the action comply to that
protocol and when it inits the view assign the delegate property to
self.
you implement myButtonAction in your view controller implementation.
and now you just do [myButton setTarget:delegate
action:#selector(myButtonAction:)
forControlEvents:UIControlEventTouchUpInside];.
I am new to IOS, Xcode and MVC. I am on a steep learning curve and am failing with what I assume is a most basic task.
I have a tabbed application with two tabs. Both tab views communicate with a web service and I want to add an image to each tab view, changing the image to indicate the connection state.
So, I created a third .xib file with a controller class (IconViewController). I am hoping to add and remove an instance of this icon view in each of the tab views.
Here is the pseudo code for my icon view:
#interface IconViewController : UIViewController
{
UIImageView *_icon;
}
#property (nonatomic) IBOutlet UIImageView *icon;
- (void)setForBusy;
- (void)setForOk;
- (void)setForFail;
And implementation:
#implementation IconViewController
#synthesize icon = _icon;
-(void)setForBusy
{
// Set Busy Icon Image
}
-(void)setForOk
{
// Set Ok Icon Image
}
-(void)setForFail
{
// Set Fail Icon Image
}
The icon IBOutlet is connected to an UIImageView on the accompanying xib file.
Here is one of the root tab controllers:
#import "IconViewController.h"
#interface TaboneViewController : UIViewController
{
IconViewController *_iconViewController;
}
#property (nonatomic) IBOutlet IconViewController *iconViewController;
and implementation:
#synthesize iconViewController = _iconViewController;
- (void)viewDidLoad
{
[super viewDidLoad];
self.iconViewController = [[IconViewController alloc]
initWithNibName:#"iconViewController"
bundle:nil];
[self.view addSubview:self.iconViewController.view];
}
In the tabView xib Interface Builder I added an Object and made it a class type IconViewController. I connected the Icon View Controller Object->Reference Outlet to the File Owner->iconViewController Outlet.
Running the project I get the error:
loaded the "iconViewController" nib but the view outlet was not set.
I have experimented with other connections but with no luck. It seems to me that my first connection should work but it doesn't.
Any idea what I am misunderstanding? Is the principle good (loading an instance of third view into two root views)? If so, what outlet needs connecting?
Many thanks, Polly
I see your issue. You want to have common stage of image for both tab. I think it is better to implement subclass of UIView (or UIImageView) and implement all methods like set (void)setForBusy and etc. The stage of image you should receive from parent ViewController, something like UINavigationView controller (if you have it). Otherwise you should save stage somewhere else. My personal opinion it is too expensive to create new controller just for your purpose.
Hope it helps.