I am making an application that uses a webService to get data in a JSON format... I get the data I parse them into a object NSArray ... and i use it .. it works fine ...
Now, if the user clicks a button I need to send him to an other Uiview ... which contains more data about the clicked object ..
The problem is here ... I don't want to request again and download the result from the server ... because i already did ... All I want is to have access to that NSArray that I have in the first UIViewController.
You can add on AnotherView.h another property:
#property (nonatomic, retain) NSArray *jsonData;
On AnotherView.m synthesize it. When you are going to to call AnotherView from InitialView, you can set jsonData with the data you retrieved on InitialView.
Create a custom initializer in your other view controller like so:
#import <UIKit/UIKit.h>
#interface OtherViewController : UIViewController
#property (nonatomic, strong) NSArray *myArray;
- (id)initWithArray:(NSArray *)anArray;
#end
Then implement it like so:
#import "OtherViewController.h"
#implementation OtherViewController
#synthesize myArray=_myArray;
- (id)initWithArray:(NSArray *)anArray {
if (!(self = [self initWithNibName:#"OtherViewController" bundle:nil]))
return nil;
if (!anArray) {
#throw [NSException exceptionWithName:#"OtherViewControllerBadInitCall" reason:#"array is nil" userInfo:nil];
}
_myArray = anArray;
return self;
}
//...
#end
You can then init and display your controller like so:
OtherViewController *otherViewController = [[OtherViewController alloc] initWithArray:greatJSONArray];
[self.navigationController pushViewController:otherViewController animated:YES];
There you go.
You can set the array as the property. You can either create a new class and set the array as the property and after you fetch the array, set the property. Or, you can create a property of the existing UIVIewController Class and pass the object.
Either way, you have to set property.
You could define a new property in your second ViewController that holds an NSArray and pass the firt array to the second ViewController before show it.
Well you have not outlined whether you send the data forward or backward. In the later case you will need to implement protocol and delegate(Define your own protocol) but for the prior case you just need to create the property of the Object you want to access in any other class. In case of web-services it is better to use protocol and delegates if u abide by the norms of MVC architecture.
Related
I'm trying to learn about delegation in Objective-C, and am having a minor issue with a variable losing it's data in the transfer process. I have Class1 that contains an NSMutableArray. The array gets populated, then I would like to transfer the array's values to Class2, and display it. Here is the relevant code in Class1:
//Class1.h
#class Class1;
// define the protocol for the delegate
#protocol Class1Delegate
#required
-(void)sayHello:(Class1 *)customClass withAntArray:(NSMutableArray *)antArray;
#end
#interface Class1 : MySuperClassName
#property (nonatomic, assign) id delegate;
-(void)helloDelegate;
#end
//Class1.m:
#interface Class1 ()
#property (nonatomic, strong) NSMutableArray *antOccurenceTimes;
#end
#implementation Class1
#synthesize antOccurenceTimes;
-(void)helloDelegate
{
// send the message to the delegate
[_delegate sayHello:self withAntArray:self.antOccurenceTimes];
}
Now, this is what I have in Class2:
#import "Class1.h"
#interface Class2 : UIView <Class1Delegate>
#end
// Class2.m:
- (void)appropriateTimeToCallMethod {
Class1 *initAntMarks = [[Class1 alloc] init];
initAntMarks.delegate = self;
[initAntMarks helloDelegate];
}
-(void)sayHello:(Class1 *)customClass withAntArray:(NSMutableArray *)antArray {
NSLog(#"Hello! %#", antArray.description);
}
The antArray.description reads as "NULL". Now, I figured that obviously it will be null, because I just created an entirely new instance of the class right before calling upon the needed method. I feel like I may have something mixed up, and being so new to delegation, I'm not sure exactly what. Does anyone know what I need to tweak to utilize Delegation?
I forgot to add that I did initialize it in Class1, and it gets populated just fine. It's only in class2 that this is occurring.
I initalize antOccuranceTimes in a separate method in ClassA in the snippet below, and the NSLog fires twice...
NSLog(#"Array initalized in class A");
antOccurenceTimes = [NSMutableArray new];
Change this line:
#property (nonatomic, assign) id delegate;
to:
#property (nonatomic, weak) id <Class1Delegate> delegate;
assign should only be used for C primitives, not Objective-c object references. You should also be checking if your object actually conforms to the delegate before messaging the delegate.
Edit:
I think you may be confused about the purpose of delegation.
Class1 *initAntMarks = [[Class1 alloc] init];
initAntMarks.delegate = self;
[initAntMarks helloDelegate];
Why are you calling a method on an object which in turn calls a delegate method when you could simply create a method that returns the NSMutableArray? The way you have your code currently set up requires that before the call to -helloDelegate you have to have filled the array with the appropriate objects. The purpose of delegation in MVC is to inform an object about an event that took place inside of another object. You are "delegating" the task off to another object, or you could say, that another object if responsible for the fulfillment of the task. Read the Apple Docs on Delegation. Delegation in your code is not the correct pattern to implement, as I stated you can simply return that array with a method call.
Edit 2:
There are two ways you can achieve this, through property methods or through an explicit method that returns your array. If you choose to use property methods, the property declaration must be in the public interface i.e. the .h file so that your class can all the accessors when the object is being implemented.
//Inside the .h
#property (nonatomic, strong) NSMutableArray *antOccurenceTimes;
This will automatically provide you with two accessor methods for the antOccurenceTimes property. These are the getter -antOccurenceTimes and setter -setAntOccurenceTimes: methods. Now after you initialize the class and fill your array you can call -antOccurenceTimes to return the array.
You can also create an explicit method that return the array:
- (NSMutableArray *)hello{
//Do something here
return _antOccurenceTimes;
}
You have not yet initialized the antOccurenceTimes. Of cause it is nil. There are many options depending on what you need. You can, for example, initialize it in a init function:
- (instancetype)init {
self = [super init];
if( self ) {
antOccurenceTimes = [NSMutableArray array];
[antOccurenceTimes addObject:#"Hello World"];
}
}
Or maybe initialize it before you call the delegate the function.
-(void)helloDelegate
{
// send the message to the delegate
self.antOccurenceTimes = [NSMutableArray array];
[self.antOccurenceTimes addObject:#"Hello World"];
[_delegate sayHello:self withAntArray:self.antOccurenceTimes];
}
I think you get my point.
I have a singleton that I'd like to use to manage the onscreen animation of my views. Here's my.
#import <Foundation/Foundation.h>
#interface OAI_AnimationManager : NSObject {
NSMutableDictionary* sectionData;
}
#property (nonatomic, retain) NSMutableDictionary* sectionData;
+(OAI_AnimationManager* )sharedAnimationManager;
- (void) checkToggleStatus : (UIView* ) thisSection;
#end
.m file
#import "OAI_AnimationManager.h"
#implementation OAI_AnimationManager
#synthesize sectionData;
+(OAI_AnimationManager *)sharedAnimationManager {
static OAI_AnimationManager* sharedAnimationManager;
#synchronized(self) {
if (!sharedAnimationManager)
sharedAnimationManager = [[OAI_AnimationManager alloc] init];
return sharedAnimationManager;
}
}
- (void) checkToggleStatus : (UIView* ) thisSection {
//get the section data dictionary
NSLog(#"%#", sectionData);
}
#end
You'll see in the .h file I added a NSMutableDictionary and am using #property/#synthesize for it's getter and setter.
In my ViewController I instantiate the animation manager as well as a series of subclasses of UIView called Section. With each one I store the data (x/y w/h, title, etc.) in a dictionary and pass that to the dictionary delcared in animation manager. In the Section class I also instantiate animation manager and add a UITapGestureRecognizer which calls a method, which passes along which section was tapped to a method (checkToggleStatus) in animation manager.
As you can I see in the method I am just logging sectionData. Problem is I am getting null for the value.
Maybe my understanding of singletons is wrong. My assumption was the class would only be instantiated once, if it was already instantiated then that existing object would be returned.
I do need all the other Section classes data as if one animates others animate in response and I can get around it by passing the tapped Section to the animation manager and doing [[Section superview] subviews] and then looping and getting the data from each that way but it seems redundant since that data is available in the ViewController when they are created.
Am I doing something wrong in trying to transfer that data? Is there a better solution? I am open to suggestions and criticisms.
Thanks
h file
#interface OAI_AnimationManager : NSObject
#property (nonatomic, retain) NSMutableDictionary* sectionData;
+(OAI_AnimationManager* )sharedAnimationManager;
- (void) checkToggleStatus : (UIView* ) thisSection;
#end
m file
static OAI_AnimationManager* _sharedAnimationManager;
#implementation OAI_AnimationManager
#synthesize sectionData = _sectionData;
+(OAI_AnimationManager *)sharedAnimationManager {
#synchronized(self) {
if (!_sharedAnimationManager) {
_sharedAnimationManager = [[OAI_AnimationManager alloc] init];
}
}
return _sharedAnimationManager;
}
- (void) checkToggleStatus : (UIView* ) thisSection {
//get the section data dictionary
NSLog(#"%#", _sectionData);
}
#end
Notice I moved your sectionData variable from the header and moved it to the implementation file. A while back, they changed it to where you can synthesize properties and specify their instance variable names along side it... hence:
sectionData = _sectionData;
I also added and underscore to the instance variable... this is a universal convention for private variables and it also will throw a compile error now if you try to type just sectionData as you did in the return statement of checkToggleStatus:. Now you either have to type self.sectionData or _sectionData.
You didn't include the code that creates an instance of your dictionary but I bet you didn't set it as self.sectionData = [[NSDictionary alloc] init] which means it would not retain the value and you would get null the next time you called it. Classic memory management mistake... I know it well because I learned the hard way hehehe
I have an application in which I have a webservice call that returns data as a dictionary. I want to access this dictionary in another view controller for loading the values into a table.
Can anybody demonstrate how to pass this response dictionary from one view controller to another?
You could define an NSDictionary property in your AnotherViewController and set it from the previous controller. I'll give a brief example below.
//.h
#interface AnotherViewController {
NSDictionary *data;
}
#property(nonatomic,retain) NSDictionary *data;
#end
//.m
#implementation AnotherViewController
#synthesize data;
Now from the current controller, after initializing AnotherViewController you set the dictionary before presenting it.
AnotherViewController *controller = [[AnotherViewController alloc] init];
controller.data = myCurrentDictionary;
Now AnotherViewController has a data property with the value of the previous controller.
Hope this helps.
I am assuming that the webservice is called because something happened (button clicked, viewDidLoad/viewDidAppear). If this is the case, passing a reference of the UIViewController to the webservice class is a perfect valid option. Keep in mind that for this relationship you should create a protocol, so on your webservice class you have something like this:
id<ViewControllerResponseProtocol> referenceToViewController;
This ViewControllerResponseProtocolwould define a method like this:
-(void)responseFromWebservice:(NSDictionary*)myDictionary;
So when the webservice class has build the NSDictionary you can the above method from the referenceToViewController:
[referenceToViewController responseFromWebservice:myDictionary];
If there isn't any kind of relationship between both, you use could NSNotificationCenter for it.
P.S: The solution of skram is perfectly valid if you already have the NSDictionary from the webservice on the initial UIViewController and now you want to pass it to a new UIViewController. Although I don't think that's what you want.
I've created a custom TablePickerViewController which is a subclass of UITableViewController. I'm using this class to display a list of object of a custom type TablePickerItem.
I'm using TablePickerViewController multiple times in my iOS application to show different kinds of lists where the user has to pick an item -- and then another view controller MainViewController should react on this selection and do something.
I've created this protocol and created a delegate property in the TablePickerViewController:
#protocol TablePickerViewControllerDelegate <NSObject>
- (void)tablePickerViewController:(TablePickerViewController *)controller
didSelectItem:(TablePickerItem*)item;
#end
When I setup a new TablePickerViewController in MainViewController it is also set as delegate -- than it will be notified when the user taps an cell in the table view.
The problem is that my MainViewController will setup multiple TablePickerViewController with different data (TablePickerItem). How should I setup my MainViewController to handle these multiple TablePickerViewController? Events from each of them will results in calling to the same protocol-method in my MainViewController.
Further I need to get the element which the TablePickerItem represents, as I need to know for instance the elements ID when acting in the tablePickerViewController:didSelectItem method. Should I just handle this by adding something like #property (nonatomic) id element to the TablePickerItem and set the original object into this property then creating it?
Maybe someone can give me an example on how to create an generic table view controller, if my solutions seems being done in the wrong way.
I'm not entirely sure of your set up, but if you have multiple pickers that feedback to the main controller then you could just have a reference to the picker e.g.
// MainViewController.m
#interface MainViewController ()
#property (nonatomic, strong) TablePickerViewController *picker1;
#property (nonatomic, strong) TablePickerViewController *picker2;
// ... and so on. Obviously you know your problem domain so you can change
// the terrible naming above to something appropriate
#end
#implementation MainViewController
// ...
- (void)theMethodWhereYouSetUpYourPickers;
{
TablePickerViewController *picker1 = [[TablePickerViewController alloc] init];
picker1.delegate = self;
self.picker1 = picker1;
// ...
}
- (void)tablePickerViewController:(TablePickerViewController *)controller
didSelectItem:(TablePickerItem*)item;
{
if (controller == self.picker1) {
NSLog(#"Something was picked in picker 1 %#", item);
} else if (controller == self.picker2) {
NSLog(#"Something was picked in picker 2 %#", item);
}
}
// ...
#end
I'm trying to set up an NSCollectionView (I have done this successfully in the past, but for some reason it fails this time).
I have a model class called "TestModel", and it has an NSString property that just returns a string (just for testing purposes right now). I then have an NSMutableArray property declaration in my main app delegate class, and to this array I add instances of the TestModel object.
I then have an Array Controller that has its Content Array bound the app delegate's NSMutableArray. I can confirm that everything up to here is working fine; NSLogging:
[[[arrayController arrangedObjects] objectAtIndex:0] teststring]
worked fine.
I then have all the appropriate bindings for the collection view set up, (itemPrototype and content), and for the Collection View Item (view). I then have a text field in the collection item view that is bound to Collection View Item.representedObject.teststring. However NOTHING displays in the collection view when I start the app, just a blank white screen. What am I missing?
UPDATE: Here is the code I use (requested by wil shipley):
// App delegate class
#interface AppController : NSObject {
NSMutableArray *objectArray;
}
#property (readwrite, retain) NSMutableArray *objectArray;
#end
#implementation AppController
#synthesize objectArray;
- (id)init
{
if (self = [super init]) {
objectArray = [[NSMutableArray alloc] init];
}
return self;
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
TestModel *test = [[[TestModel alloc] initWithString:#"somerandomstring"] autorelease];
if (test) [objectArray addObject:test];
}
#end
// The model class (TestModel)
#interface TestModel : NSObject {
NSString *teststring;
}
#property (readwrite, retain) NSString *teststring;
- (id)initWithString:(NSString*)customString;
#end
#implementation TestModel
#synthesize teststring;
- (id)initWithString:(NSString*)customString
{
[self setTeststring:customString];
}
- (void)dealloc
{
[teststring release];
}
#end
And then like I said the content array of the Array Controller is bound to this "objectArray", and the Content of the NSCollectionView is bound to Array Controller.arrangedObjects. I can verify that the Array Controller has the objects in it by NSLogging [arrayController arrangedObjects], and it returns the correct object. Its just that nothing displays in the NSCollectionView.
UPDATE 2: If I log [collectionView content] I get nothing:
2009-10-21 08:02:42.385 CollViewTest[743:a0f] (
)
The problem is probably there.
UPDATE 3: As requested here is the Xcode project:
http://www.mediafire.com/?mjgdzgjjfzw
Its a menubar app, so it has no window. When you build and run the app you'll see a menubar item that says "test", this opens the view that contains the NSCollectionView.
Thanks
The problem is that your not correctly using KVC. There is two things you can do.
Method 1: Simple but not so elegant
Use the following code to add the object to the array
[[self mutableArrayValueForKey:#"objectArray"] addObject:test];
This isn't so elegant as you have to specify the variable using a string value, so you will not get compiler warnings when spelt incorrectly.
Method 2: Generate the KVO methods needed for the array "objectArray".
Select the property in your interface declaration
Select Scripts (the script icon in the menubar) > Code > Place
accessor decls on Clipboard
Paste the declarations in the
appropriate spot in your interface file
Select Scripts > Code > Place
accessor defs on Clipboard
Paste the definitions in the
appropriate spot in your implementation file
You can then use a method that looks like
[self insertObject:test inObjectArrayAtIndex:0];