key-value-observing

问题 This question already has answers here : UITextField text change event (18 answers) Closed 3 years ago . the demo is very simple // add a textField to viewController's view UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 30, 375, 40)]; self.textField = textField; textField.placeholder = @"Please input text"; // add observer for textField's attribute "text" [textField addObserver:self forKeyPath:@"text" options:NSKeyValueObservingOptionNew |

问题 I'm trying to build a static class called Logger that will upload the log files at some point, when called like [Logger uploadLogFiles] . I'm trying to add an observer to this static class like so: [Logger addObserver:self forKeyPath:@"uploadComplete" options:NSKeyValueObservingOptionNew context:nil]; I do this just before starting an asynchronous call method for NSURLConnection. I do get a warning, saying Incompatible pointer types sending Class to parameter of type NSObject * . However,

问题 In my model I have NSMutableData Object called data. I want to observe it from another object and get a notification when data is added or removed. I understand that this is a to-many relationship, so I can't use the normal KVO by first adding the observer with this code [object addObserver:self forKeyPath:@"data" options:NSKeyValueObservingOptionNew context:NULL]; and then implement the observeValueForKeyPath:ofObject:change:context: method to do something when the notification is send. I

问题 I'm having a real pain trying to figure out why KVO is retaining all values that are being observed. Scenario: I have an NSMutableArray with weak references. (Set up with CFArrayCreateMutable and Callback having NULL for both retain and release). Meaning any object added is never retained / released. I have an NSArrayController observing values of the NSMutableArray. But now, every object of the NSMutableArray is also retained. Why is this happening and how do I stop this? 回答1: How do you

问题 I have the following code: @property (strong, nonatomic) NSMutableDictionary *todoSessionDict; @synthesize todoSessionDict; [self addObserver:self forKeyPath:@"todoSessionDict" options:NSKeyValueObservingOptionNew context:NULL]; -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { } ------------------------ NSMutableArray *unCompletedTodosArr = [NSMutableArray array]; NSMutableArray *completedTodosArr = [NSMutableArray

问题 I'm using a custom UITableViewCell to display properties of a NSMangedObject from my model. Each cell holds a reference to the managed object. I also listen to changes in properties of the object by calling addObserver:… on the object. The problem is that the objects can be removed from the model, and I want to unregister when this happens. There is a similar question here, but the suggested solution there is to use prepareForDeletion on the object, and then manually notify the cells. This is

问题 I have the following KVO observer: override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) { if context == &kvoContext { if (keyPath == "transform") { if let transform = change![NSKeyValueChangeNewKey] { print("transform: \(transform)") overlay.transform = transform as! CGAffineTransform } } } } Which prints out: transform: CGAffineTransform: {{1, 0, 0, 1}, {0, 0}} However, in my variable window I

问题 I observed the dataLayer array and I don't see any changes to push . No custom methods at all, actually. How is GTM observing the changes to the array? As far as I know, changes to an Array don't throw any events, do they? Edit: I did some more research and found Google's library for interacting with the dataLayer : https://github.com/google/data-layer-helper#listening-for-messages I'll take a look at the code and maybe even answer my own question if I understand the ineer workings. 回答1:

问题 Looking for a way to either get or calculate the wifi strength of a device? Have seen examples of scraping the status bar but cannot get it to work on iOS 11: func getSignalStrength() -> Int { let application = UIApplication.shared let statusBarView = application.value(forKey: "statusBar") as! UIView let foregroundView = statusBarView.value(forKey: "foregroundView") as! UIView let foregroundViewSubviews = foregroundView.subviews var dataNetworkItemView:UIView! for subview in

问题 I am curious about how BreezeJS is able to determine which properties of an entity have changed and still support IE8? I am in the need of similar functionality for a library I am building. JavaScript setters/getters would be the easiest solution however they are not support on non-dom objects in IE8. Are they using something like : https://gist.github.com/eligrey/384583 : or something else? 回答1: It depends on the "modelLibrary" in use, for backbone and knockout Breeze uses the "observability