I'm pretty new to the objective-c language (less than three months) but it is something that i really need to understand.
Suppose there is a controller (in a iOS environment) that manages a table view for input data from the user. The table must have editable cells and some features to make the value selection easier, for example a button that shows a popover with the possible values for a field.
Suppose there is a field to store country names. The popover first shows a list of continents; when the user selects a continent, the controller of the popover must show the countries of the previews selected continent.
Now, this popover appears in many places in the app so it will be nice if I can encapsulate it for later use. What i will expect for this popover is something like this:
...
#protocol MyPopoverDelegate<NSObject> {
-(void)didSelectCountry:(NSString *)countryName;
{
...
MyPopoverController *dataSelector = [[MyPopoverController] alloc] init];
dataSelector.dataType = CountryDataType;
dataSelector.delegate = self;
[dataSelector show];
[dataSelector release];
...
The problem here is the line [dataSelector release] because the code for managing the popover must stay alive until the country is selected. That's means the dataSelector variable must be a property of the caller class and that sucks.
The question then is:
How can i organize situations like this to have a reusable controller?
Thanks
Edited after vodkhang answer:
Ok, that's a good one, but dataSelector still is a property.
What if i do:
#implementation MyPopoverController
- (id)init {
...
[self retain];
...
}
- (void)popoverControllerDidDismissPopover: (UIPopoverController *)popoverController {
...
[delegate didFinishSelectingCountry:countryName];
[self release];
}
#end
I never see this behavior in objective-c, i feel that this is not the idea.
Why is it wrong?.
One of the way you can do for delegate method is to have:
MyPopOverDelegate
- (void)didFinishSelectingCountry:(NSString *)countryName popOver:(MyPopOver *)popOver;
Caller.m
// the caller
- (void)viewDidLoad {
MyPopoverController *dataSelector = [[MyPopoverController] alloc] init];
dataSelector.dataType = CountryDataType;
dataSelector.delegate = self;
[dataSelector show];
}
- (void)didFinishSelectingCountry:(NSString *)countryName popOver:(MyPopOver *)popOver {
// finish stuff
[popOver release];
}
This way is used a lot like NSUrlConnection, UIImagePickerController
If you want some unique object reusable across an entire app from anywhere in the view hierarchy, you can make it a property of the app delegate, and let the app delegate own it (retain it when live, release it during memory warnings, etc.).
A self retained object may eventually run into problems if you ever port your code to a garbage collected environment.
Related
I'm creating a UIPopoverController and setting "Editor1" as the content view controller.
When the caller receives the didDismissPopover I'm releasing the UIPopoverController.
This is the code:
- (IBAction)open1:(id)sender {
Editor1 *editor = [[Editor1 alloc] initWithNibName:#"Editor1" bundle:nil];
_popoverController = [[UIPopoverController alloc] initWithContentViewController:editor];
_popoverController.delegate = self;
[editor release];
[self.popOverController presentPopoverFromRect:self.open1Button.bounds inView:self.open1Button permittedArrowDirections:UIPopoverArrowDirectionAny animated:NO];
}
- (BOOL)popoverControllerShouldDismissPopover:(UIPopoverController *)popoverController{
NSLog(#"popoverControllerShouldDismissPopover");
return YES;
}
- (void)popoverControllerDidDismissPopover:(UIPopoverController *)popoverController{
NSLog(#"popvoerControllerDidDismissPopover");
[_popoverController release];
}
In my editor I have a UITextField where the user changes text and I save it when I get the message "editingDidEnd"
- (IBAction)editingDidEnd:(id)sender {
NSLog(#"Editing did End");
// SAVE PROCEDURE
}
My question regards the order in which the methods get called.
The order is:
2011-09-07 12:35:21.628 iosTest[1967:b603] popoverControllerShouldDismissPopover
2011-09-07 12:35:21.629 iosTest[1967:b603] popvoerControllerDidDismissPopover
2011-09-07 12:35:21.983 iosTest[1967:b603] Editing did End
2011-09-07 12:35:21.985 iosTest[1967:b603] viewWill Disappear
As you can see the popoverControllerDidDismissPopover gets called before editingDidEnd:, so this means I'm releasing the popover before I do my save procedure. This could bring me a crash problem.
Also, in my save procedure I need to ask the user for confirmation in some cases. I'm using a UIAlertView for this.
Do you have any recommendations?
Usually views are well-behaved and don't send events after they're off-screen. You can check for potential problems by enabling zombies (set the environment variable NSZombieEnabled=YES).
If there is a crash, the correct place to fix it is in -[Editor1 dealloc] (and possibly -viewDidUnload): just do textField.delegate = nil and you should stop receiving callbacks. This is not usually necessary except for web views and scroll views where it seems to be problematic (the scroll animation continues even if the VC is off-screen).
In your case, you can probably make saving happen in -popoverControllerShouldDismissPopover:, returning NO if you need to display a UIAlertView (and dismissing the popover when the button is pressed).
it seems, that _popoverController is the instance-property. in this case you can release it in viewDidUnload method of parent-controller.
Why don't you use UITextFieldDelegate protocol? Usage:
aTextField.delegate = self;
(...)
- (void)textFieldDidEndEditing:(UITextField *)textField {
NSLog(#"Editing did End");
// SAVE PROCEDURE
}
Read the documentation for more info.
I'm trying to make a modal view which displays the champion of my app.
there's a NSMutableString variable called champ in modal view,
which is supposed to be updated by returnChamp function in main view.
the champ string is correctly set in main view,
but in modal view, the champ value appears as (null).
In fact, it seems it doesn't even go into the returnChamp function.
so apparently something wrong with my calling or implementing returnChamp,
but I have another function that does the similar, and that works fine.
could anyone please help me?
-(void) mainView{
.....
champ = [[currentPlayers objectAtIndex:playerIndex] retain];
NSLog(#"%#",champ);
modalWinner = [[winner alloc] init];
modalWinner.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:modalWinner animated:YES];
}
- (NSMutableString *) returnChamp{
NSLog(#"returnChamp");
return champ;
}
//in modalWinner
-(void) modalView{
..............
champName = [[NSMutableString alloc] init];
NSLog(#"%#", [(MainViewController *)self.parentViewController returnChamp]);
champName = [(MainViewController *)self.parentViewController returnChamp];
UIImage *champImage = [UIImage imageNamed:champName];
}
self.parentViewController is probably not actually a reference to your object. For some reason, it seems that the framework always insists on setting a UINavigationController as self.parentViewController - even for modals, and to the extent that it will create one if there isn't already one. This is probably going unnoticed because you're casting it to your MainViewController type.
You'll need to find a different way of making your original object available to be communicated with, or perhaps pass the appropriate value to the newly-instantiated controller before you present it.
For example, if you add a champName property to the modal class, you can do:
modalWinner = [[ModalWinnerViewController alloc] init];
modalWinner.champName = myValue; /* Set value before presenting controller */
[self presentModalViewController:modalWinner animated:YES];
There will probably be some code needed to update the UI with this value. The viewWillAppear method of the modal view controller is a good place for this as it is called by the framework immediately before the view is presented.
Note that this property-based approach could be used to keep a reference to your intended parent object, as well. And see here for a different approach to solving a similar problem.
I have a function here that upon completing a single round, if your score is higher than either a default score entry or a newly placed high score then it will swap its data with your data and push everything else down. removing the last entry from the list. currently this is just one exchange and for functions sake I'm going to hard code it and then refactor it later.
My main problem is that when I set up a text input view to capture the players name execution continues immediately without the players input and crashes the game. I commented out the line that sets the text because I have a default value in place just in case any attempt that I try to make fails. How can I get Execution to wait for a moment while input is taken? Would I have to set up a delegate method? If so I'm still a bit confused by delegates. I could set it up to work but I don't understand it, so I wouldn't be able to do any other special custom tasks with it. I've worked on it for a while and got no further...
-(void)saveData:(ScoreKeep *)stats{
NSMutableDictionary *swap = [[NSMutableDictionary alloc]init];//used for swaping entries
NSString *filePath = [self pathOfFile];
NSLog(#"Writing to %#", filePath);
if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {
NSLog(#"Loading previous dictionary to save...");
dataDictionary = [NSMutableDictionary dictionaryWithContentsOfFile:filePath];
if ([dataDictionary objectForKey:#"1"]) {
NSMutableDictionary *highScore = [dataDictionary objectForKey:#"1"];
if ([stats.score intValue] > [[highScore objectForKey:#"SCORE"] intValue]) {
NSLog(#"You Win! score: %# highscore: %#", stats.score,[NSNumber numberWithInt:[[highScore objectForKey:#"SCORE"] intValue]] );
stats = [[ScoreKeep alloc] initWithNibName:#"Scorekeep" bundle:nil];
NSLog(#"Setting up name entry");
[self.view addSubview:stats.view]; //New view is added so that the player can input data(Assume it is complete);
//stats.nameTag = setName.nameTag;//This line is executed before the new view is dismissed causing an error to occur
[stats setupDictionary]; // It just goes down hill from here if the previous line is uncommented
[dataDictionary setObject:stats.sComponents forKey:#"1"];
}else {
NSLog(#"You Lose: %# highscore: %#", stats.score,[NSNumber numberWithInt:[[highScore objectForKey:#"SCORE"] intValue]] );
}
NSLog(#"Got first place entry");
}else {
NSLog(#"Initilizing Score");
}
}else{
NSLog(#"Creating new dictionary to save...");
dataDictionary = [[NSMutableDictionary alloc]init];
}
[dataDictionary writeToFile:filePath atomically:YES];
}
Help would greatly be appreciated. If more information is needed I'd be happy to provide.
by the way ScoreKeep is an object that contains a dictionary and a function to create a dictionary such that it can set any values I need and package them into sComponents(the dictionary to be entered into the main savefile)
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#class omphalosUtility;
#pragma mark -
#pragma mark Saving data
#pragma mark -
static inline void poop(){
NSLog(#"POOP");
}
I'm going to try making a utility file that works independently of the app so that I Can update files and perform other universal operations such as saving when needed. Its a step in a direction that i'd like to take.
If i get it right, (The code is really nasty, man...) your problem is that you are trying to present a View Controller with the wrong way.
Correct me if i'm wrong, is ScoreKeep is a ViewController? if so, you have to name it properly. that's for a start.
Second, you cant present another view controller only by adding its "view" property to the current view controller's View Hierarchy. that way the view will not respond properly to the events.
the correct way to to what you'r trying to do is by presenting the ScoreKeep ViewController modally.
there is no other right way to do this without using delegation. you will have to acquire this technique.
Your view controller that responsible for getting the name from the user need to have a way to tell it's master view controller that the user entered a name. and that is achieved through delegation.
What you should do:
Basically you create a protocol called something like "NamePrompterViewControllerDelegate"
that will have at least one method that will be called when the user will done entering his name.
Your ScoreKeepViewController should have an instance variable that implemented the protocol (Look at the apple documentation on protocols for assistance)
Your main view controller (the one that contains the method you added) then should implement the protocol you created, and set itself as the delegate of ScoreKeep like that:
stats = [[ScoreKeep alloc] initWithNibName:#"Scorekeep" bundle:nil];
stats.delegate = self;
For more info on presenting and dismissing ViewControllers modally you should read the documentation at Apple Documentation
I hope i helped you, there is just a lot to cover and it hardly can be done by writing an answer.
Feel free to ask more for clearance.
I want to change an image on a view, from a popup dialog of 4-6 icons (imagine like changing your image on a messenger application).
The way I implement this modal popup is by creating a new view at IB, with opacity on the background, and then I load this as a subview:
IconsViewController *iconsViewController = [[IconsViewController alloc] initWithNibName:#"IconsView" bundle:nil];
[self.view addSubview:iconsViewController.view];
So, when the user touches an icon, I have
- (IBAction)iconIsSelected:(id)sender {
switch ([sender tag]) {
case 1:
[(ParentViewController*)[self superview] changeIcon];
break;
case 2:
// same here..
break;
default:
break;
}
[self.view removeFromSuperview];
[self release];
}
The changeIcon just sets the image to a corresponding icon.
As you can guess, this is not working - the changeIcon message never works.
I can't understand what am I doing wrong, any help much appreciated!
You have a few choices here...
First one is create a property on your IconsViewController of type ParentViewController*, for example:
#property (readwrite,nonatomic,assign) ParentViewController* parentController; // weak reference
To break this down further:
readwrite because we want to be able to access the value via [self parentController] but also change it via [iconsViewController setParentController:self]
nonatomic because I'm not too worried about threading
assign to make it a "weak reference" where the parent will not be retained by the child. If they each retain the other, it could lead to memory leaks later because unless explicitly released you'd end up with a retain circle causing neither object to hit a zero retain count.
When you load from nib, set the property:
IconsViewController *iconsViewController = [[IconsViewController alloc] initWithNibName:#"IconsView" bundle:nil];
iconsViewController.parentController = self;
Then, call to it from inside of iconIsSelected like this:
[[self parentController] changeIcon];
Alternatively, you can create a delegate protocol:
#protocol IconViewSelectedDelegate (NSObject)
- (void) changeIcon;
#end
And use that protocol as a property, instead of the parent view controller type. This is more abstract, but it keeps the design cleaner. The parent view controller would then implement that delegate protocol, as one of many others.
Another option is to use NSNotificationCenter and publish/subscribe to events from your dynamic view. This is the "loosest" coupling between the two objects, but it might be overkill for this scenario.
The superview of a view is a view, not a view controller, yet you cast the superview to be of class ParentViewController. If the view has no superview, it returns nil, and message to nil are no-ops (which explains why you don't crash there).
BTW, that [self release] at the end is highly suspicious.
Iam a newbiew to iPhone development. Version of my SDK is 2.2
In my code, UIViewController is used to change view dynamically once the app is launched, a method in the UIViewController is called to know which view should be initialized along with parameters, which goes to a 'switch-case' and assign a view to current view according to the parameter, like this:
case 1:
currentView = [[View01 alloc] init];
break;
case 2:
currentView = [[View02 alloc] init];
break;
and outside the switch-case:
[self.view addSubview:currentView.view];
I wonder f can pass a parameter along with initialization, like iniWithNibName or so? I need this because have to manipulate in the leaded view, according to the view from which its called.
Thanks.
One way to approach this is to modify your View01 and View02 classes to include an initWithParam: initialiser.
i.e. add
- (id) initWithParam:(NSString *)myParam;
to the #interface section and add
- (id) initWithParam:(NSString *)myParam {
if (self = [self init]) {
// handle or store 'myParam' somewhere for use later
}
return self;
}
to the #implementation section. Notice how the initWithParam: message internally calls the existing init. Obviously you could change the type, or number of parameters passed in as required.
Another approach would be to provide a property on your view class, so you could do something like the following:
currentView = [[View01 alloc] init];
currentView.myParam = #"SomeValue";
Which approach works the best will depend somewhat on your particular application needs.