Sorry I'm still a noob and just learning to program as I go and want to start out on the right foot by learning good design up front. I am using the CLLocationManager and MKReverseGecoder to get my location. In my MKReverseGecoderDelegate method, I create my annotation to show on the MKMapView. In my callout, I use a detail disclosure indicator to bring up another UITableView that displays your current address nicely as opposed to looking at the little black callout bubble.
What is a good way for my DetailViewController (the UITableView) to get the data? Do I have my first class have ivars for address, state, zipcode. In my MKReverseGecoderDelegate, set those ivars when I get that information. (The reason I would think I would need ivars is because my method to get that information in the MKReverseGeocoderDelegate is separate from the displayDetailViewController). And then do I have my DetailViewController have those same values, and when I go to display the DetailViewController, set those same variables? It seems redundant.
Any help would be greatly appreciated. Thanks!
One option
Declare custom class inheriting NSObject like
#interface YourClassName : NSObject
{
NSString *address;
NSString *state;
NSString *zipcode;
}
#property(nonatomic, retain) NSString *address;
#property(nonatomic, retain) NSString *state;
#property(nonatomic, retain) NSString *zipcode;
#end
#implementation YourClassName
#synthesize address,state,zipcode;
-(void)dealloc
{
[super dealloc];
[address release];
[state release];
[zipcode release];
}
#end
//Create object of YourClassName and set values
YourClassName *objYourClassName = [[YourClassName alloc] init];
objYourClassName.address = #"YourValue";
objYourClassName.state = #"YourValue";
objYourClassName.zipcode = #"YourValue";
Pass this object to your DetailViewController by one method after creating method like
-(void)setDetailsForDetailViewController:(YourClassName*)pObjYourClassName
{
//self.objOfYourClassName is property declared in your detailviewcontroller.
self.objOfYourClassName = pObjYourClassName; //You can use self.objOfYourClassName to set values in TableViewController.
}
If you stuck any where let me know I would be glad to help you fix that.
If you are doing the reverse geocoding on demand, initialize the DetailViewController with the coordinate of the annotation. Something like this:
- (id)initWithCoordinate:(CLLocation*)location {
if (self = [super initWithNibName:#"DetailController" bundle:nil]) {
self.location = location;
}
return self;
}
This is a common pattern to create the controllers, because it makes it clear for the controller's user that the controller depends on a location parameter. The other alternatives (global variables, or a singleton) are not so clean because they hide information and make the controller harder to understand and unit test.
Then let the controller launch an asynchronous task to do the geocoding, set itself as delegate, and present the information when it's done.
Related
How can I access the value from an inputField located in a second viewController?
The class name of the second view controller is SettingsViewController and the outlet name for the inputField is setRateInput.
I tried this but it didn't work…
double taxRateFromInput = [[self.settings.setRateInput text]doubleValue];
when I NSLog it comes out as The value is: (null)
Any idea what I'm doing wrong?
Here is the implementation file for the main viewController:
#import "SettingsViewController.h"
#interface ViewController ()
#property (strong, nonatomic) SettingsViewController * settings;
#end
#implementation ViewController
// lazy instantiation
-( SettingsViewController *) settings
{
if (_settings == nil) {
_settings = [[SettingsViewController alloc]init];
}
return _settings;
}
- (IBAction)calculatePrice:(id)sender {
double taxRateFromInput = [[self.settings.setRateInput text]doubleValue];
#end
In theory, you could create a global. Create a new class, call it something like taxRate (.h and .m)
In taxRate.h, add the following code:
#import <Foundation/Foundation.h>
#class MyTaxRate;
#interface TaxRate : NSObject {
}
#property (nonatomic, retain) double * taxRateFromInput;
+(TaxRate*)getInstance;
#end
Then, in your controller, put a "#import taxRate.h" in there. In your .m file, add the following:
#import "TaxRate.h"
#implementation TaxRate
#synthesize taxRateFromInput;
static TaxRate *instance =nil;
+(TaxRate *)getInstance
{
#synchronized(self)
{
if(instance==nil)
{
instance= [TaxRate new];
}
}
return instance;
}
#end
Note: This is extremely similar in structure to what I'm purposing.
if you have the reference from the object view controller you can just access by the property from your attribute.
You instantiated a new SettingsViewController, but you didn't do anything to instantiate its textfield setRateInput. You can do it when you instantiate it:
_settings = [[SettingsViewController alloc]init];
_settings.setRateInput = [UITextField alloc] initWithFrame:someFrame]];
or, as a beter solution, instantiate the text field in -init of SettingsViewController
- init {
if (self = [super init] {
self.setRateInput = [UITextField alloc] initWithFrame:someFrame]];
}
return self;
}
If you use nib files, this would be a lot easier.
Note: setRateInput is a bad name for a property. Consider rateTextField instead.
Edit I forgot to add that you have to add the text field as a subview to its parent view.
So it will be like,
_settings = [[SettingsViewController alloc]init];
_settings.setRateInput = [[UITextField alloc] initWithFrame:someFrame] autorelease];
[_settings.view addSubView:_settings.setRateInput];
In this case, the setRateInput is retained by its super view. You're not using ARC, so you can call autorelease on your text field.
The better solution: Use - (void) loadView; inside SettingsViewController. Loading the view is the responsibility of the correspondent view controller.
- (void) loadView {
self.setRateInput = [[UITextField alloc] initWithFrame:someFrame] autorelease];
[self.view addSubView:_settings.setRateInput];
}
Edit: xib files and storyboards can help you out. Give these tutorials a try.
You are on the right track, also well done with your lazy instantiation (as
a demonstration that you grasped the concept, I mean).
But note, that outlets don't get connected until viewDidLoad is called. So if you
just alloc/init your viewController (lazily), the outlet to your textfield is pointing to nil.
The outlet doesnt get connected until your controller's view property is accessed, ie the view is displayed.
What you could do is give the settings viewController a handle to your calculating viewController and let it set a public property on the calculating viewController that represents the rate.
This is a common pattern - delegation - where one viewController (settingsViewcontroller) calls a method on its delegate (calculating viewController).
You wouldn't need the settingsViewcontroller property in your calculating viewController then, but just instantiate a new settings viewController every time you want it to be brought up, giving it a reference to your calculating viewController.
Another possibility - maybe even better - is to define a model object that does calculation and takes care of the rate it needs to calculate. Then you could give your settingsViewcontroller a reference to that model object (probably instantiated in your
other viewController), so that it can change the rate on it.
PS: also re think how you instantiate viewControllers generally. The designated initialiser is -initWithNibName:bundle: - so usually, you wouldn't just alloc/ -init them.
If you use storyboards (you probably should!), use storyboard's -instantiateViewControllerWithIdentifier: or use the above mentioned designated initialiser.
I'm trying to share a string between two views on my iPhone project. It currently works if I use the actual #"something here" for the string, but if I want to use something like label.text, it doesn't even though it is still a string.
I'll show you what I have to make it clearer.
First View: Info_ViewController.h
#import <UIKit/UIKit.h>
#interface Info_ViewController : UIViewController {
IBOutlet UITextField *locationField;
}
#property (nonatomic, retain) NSString *locationString;
+ (id)sharedInfoVC;
#end
First View: Info_ViewController.m
#import "Info_ViewController.h"
static Info_ViewController *sharedInfoVC = nil;
#implementation Info_ViewController
#synthesize locationString;
#pragma mark Singleton Methods
+ (id)sharedInfoVC {
#synchronized(self) {
if (sharedInfoVC == nil)
sharedInfoVC = [[self alloc] init];
}
return sharedInfoVC;
}
- (id)init {
if (self = [super init]) {
locationString = [[NSString alloc] initWithString:locationField.text]; //This is there part I mentioned earlier, when using #"something" instead of locationField.text works.
}
return self;
}
Second View: Confirm_ViewController.m
#import "Confirm_ViewController.h"
#import "Info_ViewController.h"
#implementation Confirm_ViewController
- (IBAction)buttonZ:(id)sender
{
Info_ViewController *infoVCmanager = [Info_ViewController sharedInfoVC];
locationLabel.text = infoVCmanager.locationString;
}
I put it under a button for now, but it will eventually be under viewDidLoad.
If you replace locationField.text with a string (#"blahblahblah") it won't crash and works.
When it crashes I get the error: Program received signal: "SIGABRT"
EDIT: I tried changing
initWithString:locationField.text
to
initWithFormat:#"%#",locationField.text
and now it my label in the second view prints "(NULL)"
Thanks for taking the time to give advice, I really appreciate it.
It is an error to pass nil as the format string to -[NSString initWithString].
So how are you passing nil? You actually have two instances of Info_ViewController. You have the one instance which is the normal part of your app, and then you also have a second instance which is your "singleton" (which really isn't a singleton any more).
So in your "singleton" instance, the UITextField is nil (and will always be nil) and so locationField.text is nil and you are passing that to initWithString:, which is a crash. In fact the "singleton" isn't even fully baked as view controller's go.
If you want a singleton to share data elsewhere in your app, it really should not be a Info_ViewController or any type of view controller. It should be of some other class that you use to manage your data. I would create another class and implement that as a singleton.
Hope that helps you understand what's happening here.
Pre-pend "self." to your location string.
self.locationString = [[NSString alloc] initWithString:locationField.text];
From what I understand of your code, you have got the value for locationString when you from the textfield when you initialize the viewController. At this point of time, your textfield would not be visible. After it becomes visible and you enter something, you don't have the code to store it to locationString.
What you should do is wait for Info_ViewController object to be initialized and displayed. Then on the press of some button or some other event, assign locationLabel.text from the locationString or even directly from locationField.text.
I would provide code, but I have no clue as to how you are structuring this. If you still need help, please provide the details.
I'm fairly new to programming in Objective-C. While I have been able to find my way, there now is an issue I cannot solve, which is either caused by a mistake I made or because I have a fundamental misunderstanding about classes.
Essentially, I want one class to change a variable (or object) in another class. Here is the code I have:
// LocationManager.h
#import <Foundation/Foundation.h>
#import <CoreLocation/CoreLocation.h>
#interface LocationManager : NSObject <CLLocationManagerDelegate> {
CLLocationManager *locationManager;
CLLocation *locationByCustomLocation;
}
#property (nonatomic, retain) CLLocation *locationByCustomLocation;
#end
Of course, there's a corresponding implementation file: LocationManager.m. It synthesizes the locationByCustomLocation variable.
The point is that from another class, I'd like to manipulate the locationByCustomLocation variable.
// viewCustomLocation.h
#import <UIKit/UIKit.h>
#interface viewCustomLocation : UIViewController <UITableViewDataSource, UITableViewDelegate> {
UITableView *tblLocation;
UITableViewCell *cell;
}
--
//viewCustomLocation.m
#import "viewCustomLocation.h"
#import "LocationManager.h"
#class LocationManager;
#implementation viewCustomLocation
#synthesize tblLocation;
#synthesize cell;
// some view related selectors here, but it boils down to this one:
- (void)dismissView:(id)sender
{
[self dismissModalViewControllerAnimated:YES];
LocationManager *locationManager = [[LocationManager alloc] init];
// I made sure with NSLog that the customLoc variable contains the expected data
CLLocation *customLoc = [[CLLocation alloc] initWithLatitude:place.coordinate.latitude longitude:place.coordinate.longitude];
[locationManager setLocationByCustomLocation:customLoc];
}
Now, if I use NSLog in LocationManager.m to see what's in the LocationByCustomLocation variable, I would expect the same data as in customLoc. Instead, the variable still seems empty.
I think the problem is that I created a copy of the LocationManager class, thus filling the LocationByCustomLocation variable in the copied class, rather than the original one, which is what I want. I can't figure out how to talk to the original LocationManager class.
I know of a few ways to work around this issue, but I would like to know how to achieve it this way to improve my fundamental understanding of the language.
Thanks for reading!
That's because you are allocating a new instance of LocationManager. You can either connect the two controllers between them, like declaring properties and setting them accordingly.
For example, if you instantiate controller B from controller A, you should implement a property for controller B, like firstController, so :
B *controller = [[B alloc] init];
controller.firstController = A;
and then from inside B controller, you control what happens in controller A
An alternate way is to instantiate and control everything from the ApplicationDelegate. It's a more powerful pattern.
Dear fellow programmers,
What is the best way to pass information from a child in a navigation stack up one or more levels? I have searched online and can't seem to find the best way to begin implementing this.
Specifically this is my model: I have a grouped table view with several rows. When a user clicks on a row I take them to an MVC .ie click on 'select date' row takes them to a MVC with a datepicker setup (the parent passes data to the child in the process). Once this date picker (or other piece of data) has been selected, how do I pass the data back? Heres some code of the setup if it helps:
/* following is inside didSelectRowAtIndexPath of parent in navigation stack */
if (row == 1) {
DateViewController *datevc = [[DateViewController alloc] init];
datevc.selectedDate = [self dateToEnter];
[self.navigationController pushViewController:datevc animated:YES;
[datevc release];
}
DateViewController.h
#import <UIKit/UIKit.h>
#interface EnterProcedureDateViewController : UIViewController {
IBOutlet UIDatePicker *datePicker;
NSDate *selectedDate;
}
#property (nonatomic, retain) IBOutlet UIDatePicker *datePicker;
#property (nonatomic, retain) NSDate *selectedDate;
-(IBAction)selectButtonPressed:(id)sender;
#end
DateViewController.m
#import "DateViewController.h"
#implementation EnterProcedureDateViewController
#synthesize datePicker;
#synthesize selectedDate;
-(IBAction)selectButtonPressed:(id)sender {
/* how do I pass the date pickers date back to the ivar dateToEnter of parent?? */
[self.navigationController popViewControllerAnimated:YES];
}
-(void)viewWillAppear:(BOOL)animated {
if (selectedDate == nil) {
datePicker.date = [NSDate date];
} else {
datePicker.date = selectedDate;
}
[super viewWillAppear:animated];
}
...
#end
Thanks in advance as always
Andy
UINavigationController has a property, viewControllers, which returns an NSArray of all the view controllers in the stack.
The "parent" view controller (i.e. the one below your currently visible one) can be obtained by:
TableViewController *parentViewController = (TableViewController*)[self.navigationController.viewControllers objectAtIndex:self.navigationController.viewControllers.count - 2];
You can then call any methods or set properties as required.
In call backs, one of the best and recommended ways to do it is Delegates.
In your case, you will need to create a DataViewControllerDelegate and put here all the methods that Delegates of this class can call. Now, the parent should implement this delegate and register itself as the delegate when initializing it.
It's better with an example, take a look at Jonathan's answer on making custom delegates.
Something like this?
I can't see all of your code structure, so I've made some assumptions about inheritance and class structure.
Get's the view of the parent view controller, casts it to the appropriate subclass of UIView and passes a message to it.
[((MayNeedCastToSpecificClass*)[self.view parentViewController].view) setMyDate:date];
in your parentviewcontroller add the property
#property (nonatomic, retain) NSDate *selectedDate;
in childViewController after selecting the date
parentViewController *parentViewController =[self.navigationController.viewControllers objectAtIndex:self.navigationController.viewControllers.count - 2];
parentViewController.selectedDate = self.selectedDate;
[self.navigationController popViewControllerAnimated:YES];
then you can access the property from parentviewcontroller
i'm a bit new to iphone development. I made it to develop a nice App which loads XML Data from a feed, displays this data in a UITableView and if a user taps a row there should be a detail view which displays the data.
Thats where i got stuck a little bit. It's not clear for me how to hand over the data of the entry selected by the user to my detail view. The Detail-View is called via presentModalView...
I thought about:
Calling a "setDetails:(PostingData *)myPosting" function of the viewController of my detail view.
presenting the detailView to the user by calling presentModalViewAnimated.
The view is presented, but the setDetails: function crashes without any output to the debugger console.
MY QUESTION:
What is the right way to hand over Data (in custom objects as instance of a self written class) from my view Controller to a View Controller which should display detail data.
Any hint or help is appreciated. I can't pay you for your help, but i'm on my way becoming better and then helping others too :-).
Method 1: Pass it in custom init method
In your Header File declare a property
#property (nonatomic, retain) id myDataObject;
And in your implementation use a custom init like this
-(id)initCustom:(id)myObject;
if(self = [super init]) {
myDataObject = [myObject retain];
}
return self;
}
Method 2: Use a property
Use #property in your Header
and #synthesize in your .m Implementation File
[CustomUIViewController* newViewController = [[CustomUIViewControlleralloc] init];
newViewConroller.myDataObject = myObject;
[view addSubview:newViewController.view];
[newViewController release];
define the custom object in your class. #property(nonatomic, retain) MyClass * myClass;
load the feed into a NSMutableDictionary and provide that to your class
[YOUR_VIEW_CONTROLLER *yourViewController = [[YOUR_VIEW_CONTROLLER alloc] init];
yourViewController.PROPERTY_DEFINED_BEFORE = yourObject;
[view addSubview:yourViewController.view];
[yourViewController release];
cheers