key-value-coding

问题 Is it possible to key-value code (KVC) with native Swift data structures such as Array and Dictionary? Key-Value coding is still available for NSFoundation structures within Swift, just like in Objective C. For example, this is valid: var nsarray: NSArray = NSArray() // Fill the array with objects var array: NSArray = nsarray.valueForKeyPath("key.path") But this is invalid: var swiftarray: Array = [] // Fill the array with objects var array = swiftarray.valueForKeyPath("key.path") // Invalid,

问题 This example is contrived, but it shows my point. So, if I have an object graph like the following: { sex = male; uid = 637650940; work = ({ employer = { id = 116420715044499; name = "Software Engineer"; }; "end_date" = "0000-00"; "start_date" = "0000-00"; }, { employer = { id = 188733137832278; name = "Apple"; }; }); }, //Some more objects (This is an NSArray containing NSDictionarys that have an object of type NSArray). The key field is work . I want a Key Path that will take the first

问题 Is there a way to directly access an inner-array of an an outer array in Objective-C? For example, a call to an external data source returns the following object: { bio = "this is the profile.bio data"; "first_name" = John; "last_name" = Doe; location = { name = "Any Town, Any State"; }; metadata = { pictures = { picture = "https://picture.mysite.com/picture.jpeg"; } } } I want to be able to access, for example, the location.name or the metadata.pictures.picture data. Dot notation, however,

问题 I've read a lot about NSDecimal, NSNumber, NSNumberDecimal, CFNumber... and it begins to be a kind of jungle to me. Basically, I'm trying to create a simple model class that will handle simple computations, like this one: #import <Foundation/Foundation.h> @interface Test : NSObject { float rate; float amount; int duration; } - (float)capitalizedAmount; @end @implementation Test - (float)capitalizedAmount { return (amount*pow((1.0+rate),duration)); } @end I want to access these methods and

问题 I was looking at a piece of code today and notice that this particular coder use dot notation to access instance methods (these methods don't take values, they just return value). For example: @interface MyClass : NSObject { } -(double)add; @end @implementation MyClass -(double)valueA { return 3.0; } -(double)valueB { return 7.0; } -(double)add { return self.valueA + self.valueB; } @end He did this through out his code and the compiler doesn't complain, but when I try it in my code like the

问题 I'm making a program that has a lot of constants. I decided to put them all into a separate class and I'm importing it by the classes that need it. The files look similar to this // Constants.h extern const int baseCostForBuilding; extern const int maxCostForBuilding; // etc // Constants.m const int baseCostForBuilding = 400; const int maxCostForBuilding = 1000; // etc What I'm trying to do is access them using key-value coding. What I've tried so far hasn't worked. id object = [self

问题 I have an array of UIButtons and want to set all their titles to a specific value at once, without looping through the array. The only solution I've found is by means of Key-Value Coding, i.e. something like this: [self.board setValue:@"X" forKeyPath:@"titleLabel.text"]; However, the button's titleLabel property is readonly and cannot be changed. I also tried using the button's title property as the keypath, but it doesn't work either. I've done this before by changing the "enabled" property

问题 I have a NavigationController , root view controller called "ViewController" and a second view controller called "SettingsViewController". I have a segue to the "SettingsViewController" from "ViewController" which worked until I tried to connect a UITextField called "usernameField" to the "SettingsViewController" by means of Reference Outlet. When I did I got the following error whenever I try to go to the SettingsViewController: *** Terminating app due to uncaught exception

问题 I have following code: NSMutableDictionary *dict = [NSMutableDictionary dictionary]; [defs setObject:[NSNumber numberWithInt:100] forKey:@"test1.test2.test3"]; [defs setValue:[NSNumber numberWithInt:10] forKeyPath:@"test2.test3.test4"]; I understand that setObject:forKey: creates association between "test1.test2.test3" key and given number object. On the other hand, setValue:forKeyPath: is Key-Value-Coding method that tries to locate object for path "test2.test3.test4", but in the end, it

问题 Is it possible using NSArrayController to bind a NSTextField 's value to a particular item in the array? In particular, I want to bind to a property on the first item in the array, and show nothing if the array is empty. Using arrangedObjects.command shows just "(" -- presumably it's trying to show a multi-line string with comma-separated strings for each item. I just want the first one. 回答1: Bind the text field to selection.command , and programmatically set the array controller's selection