Coding against UIKit for iPhone.
Setup, with relevant detail:
SomeView.h:
#import <UIKit/UIKit.h>
#interface SomeView : UIView {
SomeObject *myObject;
}
#property (assign) SomeObject *myObject;
-(void) doSomething;
#end
SomeView.m:
#import "SomeView.h"
#implementation SomeView
#synthesize myObject;
- (void)doSomething {
NSLog(#"doing something");
}
- (void) drawRect:(CGRect)rect {
// drawing is based on myObject
}
#end
Controller.h:
#import <UIKit/UIKit.h>
#import "SomeView.h"
#interface Controller : NSObject {
IBOutlet UIView *someView;
}
#end
Controller.m:
#import "Controller.h"
#implementation Controller
-(void)awakeFromNib {
[someView doSomething];
[someView setSomeObject:someObject];
}
#end
I am instantiating the controller object in Interface Builder, and SomeView is the class of one of my custom UIViews in my app's main window.
Now, the questions:
1) when I run the above, I get warnings for both lines: "Warning: 'UIView may not respond to 'doSomething'" and similar warning for setSomeObject. Why? (The code actually seems to work, but I don't like seeing the warnings.)
2) is this the right way of doing things? What I am really after, is making SomeView aware of someObject, so that when drawRect for SomeView is called, it can change its behavior based on current state of someObject. I don't need to have the object directly in SomeView; I could have it in the controller, but the view still needs some information from it that may change at runtime.
You declared someView as an instance of UIView, but doSomething is a method of SomeView. So it is correct — the class you told the compiler that the variable points to does not respond to that message. If you don't want warnings, you'll have to make it a SomeView * instead of a UIView *.
Otherwise, your general architecture looks OK to me.
Related
I am a newbie to iPhone development and have some basic questions to ask about protocols and delegates. I have two view controllers: view controller and viewcontroller2nd. I have UITextField in one of them and would like to type something (like a name) in it and in the viewcontroller2nd, I have a UILabel and i would like it to appear Hello, name when the UITextField is changed.
I am following this video: http://www.youtube.com/watch?v=odk-rr_mzUo to get the basic delegate to work in a single view controller.
I am using protocols to implement this:
SampleDelegate.h
#import <Foundation/Foundation.h>
#protocol ProcessDelegate <UITextFieldDelegate>
#optional
- (BOOL)textFieldShouldReturn:(UITextField *)textField;
#end
#interface SampleDelegate : NSObject
{
id <ProcessDelegate> delegate;
}
#property (retain) id delegate;
#end
SampleDelegate.m
#import "SampleDelegate.h"
#implementation SampleDelegate
#synthesize delegate;
- (BOOL)textFieldShouldReturn:(UITextField *)textField{
lbl.text = [NSString stringWithFormat:#"Hello, %#",txtField.text];
[txtField resignFirstResponder];
}
#end
ViewController.h
#import <UIKit/UIKit.h>
#import "SampleDelegate.h"
#interface ViewController : UIViewController <ProcessDelegate>
{
IBOutlet UITextField *txtField;
}
#end
Viewcontroller.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
ViewController2nd.h
#import <UIKit/UIKit.h>
#interface ViewController2nd : UIViewController <ProcessDelegate> {
IBOutlet UILabel *lbl;
}
#end
and ViewController2nd.m is standard code from Xcode.
My question is how do i link my delegate function to my viewcontroller and viewcontroller2nd to get it working?
Pardon me if the question is stupid.. Need some guidance. Do point me any other mistakes that i am doing as well.. Thanks..
Your delegation is a bit... Off.
Firstly: Don't override UIKit delegate methods through protocol inheritance. It's pointless. Why not just make your class conform to the specified delegate in the first place?
#protocol ProcessDelegate //No more protocol inheritance!
//...
#end
Secondly: When an object has defined a protocol, a valid instance of that object must be in use by its delegate (or at least passed to it). So, anything that wants to be the delegate of SampleDelegate (really a bad name for a class, by the way) would initialize a valid SampleDelegate object, and call -setDelegate: as though it were any other property.
//#import "SampleDelegate"
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//make this a property, so it isn't crushed when the function exits.
SampleDelegate *myDelegateObject = [[SampleDelegate alloc]init];
[myDelegateObject setDelegate:self]; //conform to the delegate
}
Thirdly: You don't actually define any delegate methods! What's the point of delegation if there's nothing to delegate!l
#protocol ProcessDelegate
-(void)someMethod;
#end
Fourth, and most important: Never, ever, ever, ever use the retain, or strong storage specifiers with a delegate! Delegate objects are supposed to be weak or assign to prevent nasty retain cycles.
#property (assign, nomatomic) id delegate;
I'm a relatively new iPhone developer and am making great progress building my 2nd iPhone app. In the app I'm building now I'm doing some code separation with some protocols and delegates so that I car re-use some of my code in a variety of places throughout my code.
Here's what I want to happen:
CITRootViewController creates an instance of a CITReportCreator class, passing itself as a property so that the reportCreator can open additional view controllers and such.
CITReportCreator class is declared as implementing the CITImageCaptureDelegate protocol, which is declared in the CITImageCaptureViewController file.
CITImageCaptureViewController defines the delegate protocol and has a method that passes back data and references to the child view controller so that CITReportCreator can interact with it's data, close the related XIB, etc.
I believe I'm getting the delegate and protocol established correctly, and verified that my 'delegate' object still contains data when it is called, but I'm getting a EXC_BAD_ACCESS method when my view controller tries to pass data back to the delegate in this line of code:
[self.delegate childViewControllerDidFinish:self];
Here's a good portion of the rest of my code. I had this working by using CITRootViewController as my delegate instead of the CITReportCreator class, but now that I'm separating the code, something has broke.
CITReootViewController.m (the view controller that calls the Report Creator)
//create a nrew report
-(IBAction)createReport:(id)sender {
CITReportCreator *report = [CITReportCreator alloc];
[report createNewReport:self];
}
CITReportCreator.h
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import "CITImageCaptureViewController.h"
#interface CITReportCreator : NSObject <CITImageCaptureDelegate>
#property (strong, nonatomic) NSArray *imageList;
#property (nonatomic) NSInteger imageIndex;
-(int) createNewReport:(UIViewController *)parent ;
//Delegate Methods
-(void) childViewControllerDidFinish:(UIViewController*)viewController;
#end
And CITReportCreator.m
#import "CITReportCreator.h"
#implementation CITReportCreator
{
UIViewController *parentController;
}
#synthesize imageList;
#synthesize imageIndex;
-(int) createNewReport:(UIViewController *)parent
{
//store a reference to the parent view controller
parentController = parent;
// init code....
//head to the first image capture view
[self startImageCapture];
return 0;
}
-(int)startImageCapture
{
//pull the image name from the array of images
NSString *imageName = [imageList objectAtIndex:imageIndex];
//prep the image capture controller
CITImageCaptureViewController *capture = [[CITImageCaptureViewController alloc] initWithNibName:#"CITImageCaptureViewController" bundle:nil];
//Assign the capture controller's delegate
capture.imageName = imageName;
capture.delegate = self;
//Display the capture controller
[parentController presentModalViewController:capture animated:YES];
return 0;
}
//a break point set here never gets hit.
-(void) childViewControllerDidFinish:(UIViewController*)viewController;
{
[viewController dismissModalViewControllerAnimated:YES];
}
#end
And finally, the CITImageCaptureViewControllers
CITImageCaptureViewController.h
#import <UIKit/UIKit.h>
#protocol CITImageCaptureDelegate <NSObject>
-(void) childViewControllerDidFinish:(UIViewController*)viewController;
#end
#interface CITImageCaptureViewController : UIViewController
{
id<CITImageCaptureDelegate> delegate;
}
#property (nonatomic,assign) id<CITImageCaptureDelegate> delegate;
#property (nonatomic, assign) NSString *imageName;
//continue button pressed method
-(IBAction)continueButtonPressed:(id)sender;
#end
And the .m file
#import "CITImageCaptureViewController.h"
#interface CITImageCaptureViewController ()
#end
#implementation CITImageCaptureViewController
#synthesize navItem;
#synthesize imageName;
#synthesize delegate = _delegate; //i think this may be part of the problem
//cutting out initWithNibName, viewDidLoad, etc...
- (IBAction)continueButtonPressed:(id)sender
{
[self.delegate childViewControllerDidFinish:self];
}
#end
I find nothing with delegates and protocols all that simple, but I'm guessing I'm missing a small change somewhere. Can you help me head in the right direction?
I have a class called ToolbarView which is a subclass of UIView and basically creates a UIView that has a disappearing / reappearing UIToolbar on top. I also have a subclass of ToolbarView called DraggableToolbarView enables the user to drag the view around the screen.
I need to create a delegate for ToolbarView so it can notify another object / class of when the toolbar reappears and disappears. I also need to create a delegate for DraggableToolbarView so I can notify another object / class when the view is dragged. DraggableToolbarViews delegate will also need to notify another object / class of when the toolbar reappears and disappears.
So I decided to implement ToolbarViewDelegate, and have DraggableToolbarViewDelegate inherit from it and have its own method like following:
ToolbarView.h
#import <UIKit/UIKit.h>
#protocol ToolbarViewDelegate;
#interface ToolbarView : UIView <UIGestureRecognizerDelegate>
{
id <ToolbarViewDelegate> _toolbarViewDelegate;
}
#property(nonatomic, assign) id <ToolbarViewDelegate> toolbarViewDelegate;
#end
ToolbarView.m
#import "ToolbarView.h"
#import "ToolbarViewDelegate.h"
...
- (void) showBars
{
...
if (self.toolbarViewDelegate)
{
[self.toolbarViewDelegate toolbarViewWillShowToolbar:self];
}
...
}
- (void) hideBars
{
...
if (self.toolbarViewDelegate)
{
[self.toolbarViewDelegate toolbarViewWillHideToolbar:self];
}
...
}
ToolbarViewDelegate.h
#class ToolbarView;
#protocol ToolbarViewDelegate
#required
- (void) toolBarViewWillShowToolbar:(ToolbarView *)toolbarView;
- (void) toolBarViewWillHideToolbar:(ToolbarView *)toolbarView;
#end
DraggableToolbarView.h
#import "ToolbarView.h"
#protocol DraggableToolbarViewDelegate;
#interface DraggableToolbarView : ToolbarView
{
id <DraggableToolbarViewDelegate> _draggableToolbarViewDelegate;
}
#property(nonatomic, assign) id <DraggableToolbarViewDelegate> draggableToolbarViewDelegate;
#end
DraggableToolbarView.m
#import "DraggableToolbarView.h"
#import "DraggableToolbarViewDelegate.h"
...
- (void)drag:(UIPanGestureRecognizer *)sender
{
...
if (self.draggableToolbarViewDelegate)
{
[self.draggableToolbarViewDelegate draggableToolbarViewWillDrag:self];
}
...
}
...
DraggableToolbarViewDelegate.h
#import "ToolbarViewDelegate.h"
#class DraggableToolbarView;
#protocol DraggableToolbarViewDelegate <ToolbarViewDelegate>
#required
- (void) draggableToolbarViewWillDrag:(DraggableToolbarView *)draggableToolbarView;
#end
SomeViewController.h
#import <UIKit/UIKit.h>
#import "ToolbarViewDelegate.h"
#import "DraggableToolbarViewDelegate.h"
#interface SomeViewController : UIViewController <ToolbarViewDelegate, DraggableToolbarViewDelegate>
{
}
#end
SomeViewController.m
#import "DraggableToolbarView.h"
...
- (void) toolbarViewWillShowToolbar:(ToolbarView*)toolbarView
{
//NSLog(#"Toolbar Showed");
}
- (void) toolbarViewWillHideToolbar:(ToolbarView*)toolbarView
{
//NSLog(#"Toolbar Hidden");
}
- (void) draggableToolbarViewWillDrag:(DraggableToolbarView*)draggableToolbarView
{
//NSLog(#"Dragged");
}
...
[draggableToolbarView setDraggableToolbarViewDelegate:self];
...
When I do this only the DraggableToolbarDelegate methods are responding. However when I also do [drabbleToolbarView setToolbarViewDelegate:self] it works. I've tried doing each delegate separately without inheritence and it works fine so I believe the problem isn't in any other part of the code.
Anyone might know why? I figured by making the protocols inherit, I wouldn't also have to set the ToolbarViewDelegate for a DraggableToolbar object.
UPDATE: Added a lot more code
In your code, any given DraggableToolbarView instance has two properties to connect to delegates, one called toolbarViewDelegate which it inherits from its superclass, and one called draggableToolbarViewDelegate which is defined in DraggableToolbarView itself. You've got to set both of those if you want the controller to get all the delegate messages.
What you're trying to do is possible, however. You need to use the same property name in both your view classes, so that there is only one delegate connection for any instance.
First, change the name of the delegate in the superclass. (Note that you don't need, and indeed shouldn't bother, to declare an ivar for the property -- it's created by #synthesize.)
#interface ToolbarView : UIView <UIGestureRecognizerDelegate>
#property (nonatomic, assign) id <ToolbarViewDelegate> delegate;
#end
You will use the same property name in the subclass.
#interface DraggableToolbarView : ToolbarView
#property (nonatomic, assign) id <DraggableToolbarViewDelegate> delegate;
#end
This is allowed as long as the name of the backing ivar in the subclass is different than that of the superclass, e.g.,
// In superclass
#synthesize delegate;
// In subclass
#synthesize delegate = delegate_;
Now change all the delegate messages in the two view classes to use this one property:
- (void)showBars
{
if (self.delegate)
{
[self.delegate ...
- (void)drag:(UIPanGestureRecognizer *)sender
{
//...
if (self.delegate)
{
[self.delegate ...
Now you can send setDelegate: to a DraggableToolbarView and it will use the same delegate for the dragging methods and the show/hide methods.
Finally, a terminology/explanatory note. In response to your previous question, Caleb used the correct term for "stacked" protocols, and Richard did not. Protocols don't inherit from each other, but one protocol can adopt the other. The relationship is similar, but distinct. When an object conforms to a protocol, it promises to implement the methods declared in that protocol. No implementation comes along with the protocol. The same is true of one protocol adopting the other -- the methods are just declared to exist in both. When you write:
#protocol DraggableToolbarViewDelegate <ToolbarViewDelegate>
you are saying that any object which promises to implement DraggableToolbarViewDelegate's methods will also implement the methods from ToolbarViewDelegate. That's all that it means. Again, no implementation comes along with that promise.
In this case, that means that a DraggableToolbarView can expect its delegate to implement the methods in ToolbarViewDelegate.
You have not given the entire code, but from whatever is out here,
Make sure that
Your ToolBarView and its subclasses have an id <ToolBarViewDelegate> delegate as a property.
Your DraggableToolbarViewDelegate extends NSObject protocol.
and your other ViewController object conforms to delegate protocol and not the toolbarview.
Once your controller gives implementation of delegates methods and conforms to the protocol, set the delegate of view's object to self and then use delegate property set in the view to call these protocol methods.
//
// MyGameViewController.h
//
#import < UIKit/UIKit.h >
#import "SecondViewController.h"
#interface MyGameViewController : UIViewController {
IBOutlet SecondViewController *secondViewController;
}
-(IBAction)goToSecondView;
#end
//
// MyGameViewController.m
//
#import "MyGameViewController.h"
#implementation MyGameViewController
-(IBAction)goToSecondView{
[self presentModalViewController:secondViewController animated:YES];
}
//
// MyGameView.h
//
#import < UIKit/UIKit.h >
#import "Sprite.h"
#interface MyGameView : UIView {…}
Currently I have implemented a button on the MyGameView.xib to invoke the secondViewController view and it works. But I want the secondViewController get invoked by programming inside MyGameView.m when there is interruption, not by pressing a button. Therefore, I think there are 2 approaches:
a) Either make the goToSecondView method available to MyGameView.m
b) Implement all the code in MyGameViewController.h and MyGameViewController.m to MyGameView.m.
Issues:
1) When tried to make a) happen, I have to make goToSecondView method starting with (void), not (IBAction). But then how to invoke it in MyGameView.m?
2) I tried to do b) and implemented all code to MyGameView.m. But presentModalViewController is a method of ViewController and does not work in UIView. So what is the solution?
As you stated, you can't call presentModalViewController in a UIView class. This seems like a great opportunity to use a delegate. You could do something along the lines of:
In MyGameView.h
#protocol MyGameViewDelegate
- (void)showSecondView;
#end
#interface MyGameView {
}
#property (nonatomic, assign) id <MyGameViewDelegate> delegate;
...
#end
In MyGameView.m, when you need to show the second view:
[self.delegate showSecondView];
In MyGameViewController.h:
#import "MyGameView.h"
#interface MyGameViewController : UIViewController <MyGameViewDelegate> {
...
In MyGameViewController.m:
#pragma mark MyGameViewDelegate methods
- (void)showSecondView {
[self goToSecondView];
}
Note that you'll also need to set MyGameViewController to be the delegate of MyGameView. You could do that in Interface Builder, or in code, depending on where you create the two objects.
To do it in code, for example in the MyGameViewController.h viewDidLoad method:
myGameView.delegate = self;
I try to learn protocol of objective C.
I write two files, the first one is FirstViewController.h, and in which there is a protocol "print". I declare FirstViewController class in successViewController with the delegate method "print".
The question is why the console output is "C". Why I can not get the "B" output? Why the protocol method did not perform?
#import <UIKit/UIKit.h>
#import "FirstViewController.h"
#interface successViewController : UIViewController <FirstViewControllerDelegate> {
}
#end
#import "successViewController.h"
#import "FirstViewController.h"
#implementation successViewController
- (void)viewDidLoad {
FirstViewController *firstViewController= [[FirstViewController alloc] init];
firstViewController.delegate=self;
NSLog(#"C");
[super viewDidLoad];
}
-(void) print{
NSLog(#"B");
}
#end
#import <Foundation/Foundation.h>
#class FirstViewController;
#protocol FirstViewControllerDelegate <NSObject>
- (void) print;
#end
#interface FirstViewController : NSObject {
id <FirstViewControllerDelegate> delegate;
}
#property (nonatomic, assign) id <FirstViewControllerDelegate> delegate;
#end
#import "FirstViewController.h"
#implementation FirstViewController
#synthesize delegate;
#end
Because you never call the print method. Where were you expecting it to be called?
Objective-C protocols allow you to specify that a class is capable of performing certain actions. In your example, the successViewController is declared FirstViewControllerDelegate, meaning it is capable of handing the duties required by FirstViewController of its delegate. It is more of a programming contract between classes, one that can be verified by the compiler.
As a side note, classes in Objective-C should always start with a capital letter, methods should always start lowercase. Your FirstViewController follows this rule, but the successViewController does not.
You need to call the method you want to use.
[successViewController print];
You never call the delegates print method. A delegate can not read your mind and automagically call stuff. Lets take a small example how how delegates are supposed to work.
Assume we have a class called Delay, the only thing it do is to wait for a time when start is called, and then tell it's delegate that it has waited. Optionally the delegate can tell the Delay how long to wait, if the client do not care, a 1 second delay is assumed.
Some rules:
First argument of all delegate methods should be the sender itself, never have delegate methods with no arguments.
Delegate method name should include one of the words:
will - if method is called before something unavoidable occurs. Example applicationWillTerminate:
did - if method is called after something has occurred. Example scrollViewDidScroll:
should - if the method return a BOOL to signal if something should occur. Example textFieldShouldClear:
Name the method to tell what has occurred, not what you expect the delegate to do.
Only exception is if the client is expected to return something, then that something should be part of the name. Example: tableView:editingStyleForRowAtIndexPath:
Here is the simple definition and implementation. Notice that I do not even check if the delegate has been set, since calling methods on nil is just ignored anyway.
// Delay.h
#protocol DelayDelegate;
#interface Delay : NSObject {
#private
id<DelayDelegate> _delegate;
}
#property(nonatomic, assign) id<DelayDelegate> delegate;
-(void)start;
#end
#protocol DelayDelegate <NSObject>
#required
-(void)delayDidComplete:(Delay*)delay;
#optional
-(NSTimeInterval)timeIntervalForDelay:(Delay*)delay;
#end
// Delay.m
#interface Delay
#synthesize = delegate = _delegate;
-(void)start {
NSTimeInterval delay = 1.0;
if ([self.delegate respondsToSelector:#selector(timeIntervalForDelay:)]) {
delay = [self.delegate timeIntervalForDelay:self];
}
[self performSelector:#selector(fireDelay) withObject:nil afterDelay:delay];
}
-(void)fireDelay {
[self.delegate delayDidComplete:self];
}
#end