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
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.
im new to IOS and Objective-C and the whole MVC paradigm and i'm stuck with the following.
I am working on (replica) Contact app, also available in iphone as build in app. i want to pass data through another view controller and the data is pass (null) :(.
My Question is, How do I transfer the data from one view to another?
As most the answers you got, passing data between one controller and another just means to assign a variable from one controller to the other one.
If you have one controller to list your contacts and another one to show a contact details and the flow is starting from the list and going to detail after selecting a contact, you may assign the contact variable (may be an object from the array that is displayed in your list) and assign it to the detail view controller just before showing this one.
- (void)goToDetailViewControllerForContact:(Contact *)c
{
ContactDetailViewController *detailVC = [[[ContactDetailViewController alloc] init] autorelease];
detailVC.contact = c;
[self.navigationController pushViewController:c animated:YES];
//[self presentModalViewController:detailVC animated:YES]; //in case you don't have a navigation controller
}
On the other hand, if you want to insert a new contact from the detail controller to the list controller, I guess the best approach would be to assign the list controller as a delegate to the detail one, so when a contact is added the delegate is notified and act as expected (insert the contact to the array and reload the table view?).
#protocol ContactDelegate <NSObject>
- (void)contactWasCreated:(Contact *)c;
// - (void)contactWasDeleted:(Contact *)c; //may be useful too...
#end
#interface ContactListViewController : UIViewController <ContactDelegate>
#property (nonatomic, retain) NSArray *contacts;
...
#end
#implementation ContactListViewController
#synthesize contacts;
...
- (void)goToDetailViewControllerForContact:(Contact *)c
{
ContactDetailViewController *detailVC = [[[ContactDetailViewController alloc] init] autorelease];
detailVC.contact = c;
detailVC.delegate = self;
[self.navigationController pushViewController:c animated:YES];
//[self presentModalViewController:detailVC animated:YES]; //in case you don't have a navigation controller
}
- (void)contactWasCreated:(Contact *)c
{
self.contacts = [self.contacts arrayByAddingObject:c]; //I'm not sure this is the correct method signature...
[self reloadContacts]; //may be [self.tableView reloadData];
}
...
#end
#interface ContactDetailViewController : UIViewController
#property (nonatomic, assign) id<ContactDelegate> delegate;
...
#end
#implementation ContactDetailViewController
#synthesize delegate; //remember to don't release it on dealloc as it is an assigned property
...
- (void)createContactAction
{
Contact *c = [[[Contact alloc] init] autorelease];
[c configure];
[self.delegate contactWasCreated:c];
}
...
#end
Technically, you shouldn't!
The whole idea is not for "views" to control what happens to the data.
What you want to do is to pass data between controllers (which I imagine is exactly what you are planning to do anyway).
You can have shared model (an instance of an object that both view controllers would access) keeping the data you want to share,
You can use notifications to pass data (it is best suited for certain cases).
You can write something to disk and read it again later.
You can use NSUserDefaults.
You can use KeyChain.
...
The best way is:
declare the appropriate #property in the second view controller
when you create it, simply set the property with
viewController.property = valueYouWantToPass;
I'm a big fan of delegates and protocols.
And in some occasions use a Singleton pattern.
two ways to pass/share data between view controller
create an object and sent the data like this
QGraduteYr *tableverify=[[QGraduteYr alloc]initWithStyle:UITableViewStyleGrouped];
tableverify.mystring=myString
[self.navigationController pushViewController:tableverify animated:YES];
another method is stor it in the delegates and use it via shared delegates
MedicalAppDelegate *appdelegate=(MedicalAppDelegate *)[[UIApplication sharedApplication]delegate];
appdelegate.collnameStr=collStr;
and ust this appdelegates value whereever you need
I am building a utility-based application, the data is stored in the MainViewController, and now I know how to pass data to the FlipsideViewController (many regards to this thread BTW, Sending data from Mainview to Flipside?). But I am getting the data onto an subview (subclass of UIView) that I have added to the flipside view. How can I pass data to this subview? I saw there is already a delegate and protocol set up in the FlipsideViewController.h, I am really new to the delegate sort of things. Any help would be greatly appreciated!
Updates:
On the main view, I have a couple of text fields for users to input to create an object. All the objects are stored in an array. Namely, my data is created and stored in the MainViewController. Now on the flip side, I have a custom UIView subclass which allows me to do my own drawing based on the data in that array. What I need to do here is pass the data that stored in MainViewController to this subview. Here is my relevant code:
In the MainViewController.m
- (IBAction)showInfo:(id)sender {
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.delegate = self;
controller.receiver = data;//this is what I've done.
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
}
In the FlipsideViewController.h
#protocol FlipsideViewControllerDelegate;
#interface FlipsideViewController : UIViewController {
id <FlipsideViewControllerDelegate> delegate;
DataModel *receiver; //create a property to receive the data transferred from main view
}
#property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;
#property (nonatomic, retain) DataModel *receiver;
- (IBAction)done:(id)sender;
#end
#protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
#end
In the above code, "data" is an DataModel object declared in the MainViewController.h file.
And I want to do my custom drawing in drawing class (subclass of UIView), how can I pass data from the FlipsideViewControllerto this subview? Do I need to make use of delegate declared in the FlipsideViewController.h file? Thanks in advance!
I have had a quick look at the template and think you are getting confused with what the delegate is being used for.
The delegate in this template is not transferring data. When you have clicked the done button it calls back to MainViewController and asks it to call the dismissModalViewControllerAnimated method so that it can remove the view controller. This seems a bit superflous as the documentation states
If you call this method on the modal view controller itself, however, the modal view controller automatically forwards the message to its parent view controller.
Therefore you don't really need to call the parent to do this.
In Interface builder you can see that the FlipsideView.xib has it's File's Owner set to FlipsideViewController.xib.
Now if you right click the File's Owner you will see that view is connected to View this basically means that view is the name of the property in FlipsideViewController and View is the element in Interface Builder.
Therefore we can access elements in the xib file from FlipsideViewController using outlets.
To say draw a label you will need to do a couple of things
First add a property in the .h and synthesize it in the .m like
// FlipsideViewController.h
#interface FlipsideViewController : UIViewController
#property (nonatomic, retain) IBOutlet UILabel *testLabel; // <----- Added this
#property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;
- (IBAction)done:(id)sender;
#end
// FlipsideViewController.m
#implementation FlipsideViewController
#synthesize delegate = _delegate;
#synthesize testLabel = _testLabel; // <----- Added this
// More methods
- (void)dealloc
{
[_testLabel release]; // Always do you memory management
[super dealloc];
}
Then back in Interface Builder
Add a UILabel element to your view
ctrl + drag from File's Owner to the UILabel you added
Select the label in my example it is testLabel
Now these are hooked up correctly. The place where you want to be setting the value of the label is in viewDidLoad: which you can now do like this
- (void)viewDidLoad
{
[super viewDidLoad];
self.testLabel.text = #"It Works"; // You would use the data passed in from `MainViewController`
}
I find the easiest way to pass data from one view to another is by directly setting the data in the next view from the original view.
For example;
In your FlipsideViewController.h, declare a 'container' for the data you want to pass. It must be the same class on both sides to work properly, ie. NSArray to NSArray, NSMutableDictionary to NSMutableDictionary.
NSMutableArray *newData;
...
#property (nonatomic, retain) NSMutableArray *newData; // This allows you to access this object from outside this class.
and in FlipsideViewController.m
#synthesize newData;
...
[newData release];
Now we need to pass the data, so to speak. Let's say the data we want to 'send' is stored in a NSMutableArray called 'results'.
In our MainViewController.m, when we are instantiating our next view controller (in this case FlipsideViewController) we can directly reference the newData mutable array after we initalize the nib.
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.newData = results;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
Make sure you are importing your FlipsideViewController in your MainViewController.h file.
If the property is declared in your .h file, you can pretty much reference the contents of the object from anywhere within the view stack!
Hope that helps :D
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.
I am getting data from NSTextField, and saving data in NSMutableArray. I want to show the same data in another class which in child of UITableViewController.
How can I show data of NSMutableArray to myTableView which is another class??
Help me out, please
Surely, I will appraise if I found proper way.
Your tableView is in a MyViewController class. You need to create a NSMutableArray *sourceArray attribute on that class, as well as the associated property, using for instance:
#property (nonatomic, retain) NSMutableArray *sourceArray;
Then when you instantiate this View Controller or whenever you make it appear, assign the results to sourceArray :
MyViewController *mvc = [[MyViewController alloc] initWith...];
mvc.sourceArray = theResult;
[self presentModalViewController:mvc animated:YES];
[mvc release];
Then use the sourceArray as the Table View datasource.
Make a property of NSMutableArray in app delegate class and assign the result of the source array to it as soon as you fetch any result, because you can access its instance all over your project.