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POObj-C - How to pass data between viewcontrollers using a singleton?
 

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    <p>Alright, so this is an extension to a question I asked last night. I have a little firmer grasp on how data can be passed between view controllers using various techniques. I wanted to go the MVC route, and creating a Singleton class seems the closest concept similar to MVC.</p> <p>Basically I created a simple app with two View Controllers and a singleton class. I am trying to pass the value of a text field into a UILabel. For whatever reason it isn't working. This is what my code looks like.</p> <p><strong>ViewController.h</strong></p> <pre><code>#import &lt;UIKit/UIKit.h&gt; #import "Model.h" #import "ViewController2.h" @interface ViewController : UIViewController { NSString *text2pass; } @property (weak, nonatomic) IBOutlet UITextField *tf; @property (weak, nonatomic) IBOutlet UILabel *btn; - (IBAction)go:(id)sender; @end </code></pre> <p><strong>ViewController.m</strong></p> <pre><code> #import "ViewController.h" @interface ViewController () @end @implementation ViewController @synthesize tf = _tf; @synthesize btn = _btn; - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. NSString *tfstring = _tf.text; NSLog(@"string = %@",tfstring); } - (void)viewDidUnload { [self setTf:nil]; [self setBtn:nil]; [super viewDidUnload]; // Release any retained subviews of the main view. } - (IBAction)go:(id)sender { NSLog(@"btn pressed"); UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil]; ViewController2 *vc2 = (ViewController2 *) [storyboard instantiateViewControllerWithIdentifier:@"home"]; text2pass = _tf.text; [self passValues]; [self presentModalViewController:vc2 animated:YES]; } -(void) passValues { Model *model = [Model sharedModel]; model.passedText = text2pass; } @end </code></pre> <p><strong>ViewController2.h</strong></p> <pre><code>#import &lt;UIKit/UIKit.h&gt; #import "ViewController.h" @interface ViewController2 : UIViewController { NSString *passedText; } @property (nonatomic)NSString *passedValue; @property (weak, nonatomic) IBOutlet UILabel *lbl; - (IBAction)back:(id)sender; @end </code></pre> <p><strong>ViewController2.m</strong></p> <pre><code>#import "ViewController2.h" @interface ViewController2 () { NSString *passedtext; } @end @implementation ViewController2 @synthesize lbl = _lbl; @synthesize passedValue = _passedValue; - (void)viewDidLoad { // do code stuff here NSLog(@"passedText = %@",passedText); _lbl.text = passedText; [super viewDidLoad]; } - (void)viewDidUnload { [self setLbl:nil]; [super viewDidUnload]; // Release any retained subviews of the main view. } - (IBAction)back:(id)sender { UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:nil]; ViewController *vc = (ViewController *) [storyboard instantiateViewControllerWithIdentifier:@"welcome"]; [self presentModalViewController:vc animated:YES]; } @end </code></pre> <p><strong>Model.h</strong></p> <pre><code>#import &lt;Foundation/Foundation.h&gt; @interface Model : NSObject { NSString *passedText; } @property (nonatomic, strong) NSString* passedText; + (Model *) sharedModel; @end </code></pre> <p><strong>Model.m</strong></p> <pre><code>#import "Model.h" @implementation Model @synthesize passedText = _passedText; static Model *sharedModel = nil; + (Model *) sharedModel { @synchronized(self){ if (sharedModel == nil){ sharedModel = [[self alloc] init]; } } return sharedModel; } @end </code></pre> <p>The project can be downloaded in its entirety from here <a href="http://chrisrjones.com/files/KegCop-Test.zip" rel="nofollow">http://chrisrjones.com/files/KegCop-Test.zip</a></p> <p>If you know why the UILabel is not displaying the text field text let me know. Oh I pretty much followed this -> <a href="http://www.youtube.com/watch?v=ZFGgMPcwYjg&amp;feature=plcp" rel="nofollow">http://www.youtube.com/watch?v=ZFGgMPcwYjg&amp;feature=plcp</a></p>
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