objective-c-category

问题 I am trying to plan how to add a couple methods to all instances of certain objects. I think adding a category to the parent object(UIViewController) would work for what I want to do, but can I override a method added this way? Most of the time the subclasses will use the default methods but I do know I will need to override the method at least once. Also what other methods should I consider for what I am trying to do? Example of what I am trying to do: I have a set of Objects that act like

问题 I am trying to plan how to add a couple methods to all instances of certain objects. I think adding a category to the parent object(UIViewController) would work for what I want to do, but can I override a method added this way? Most of the time the subclasses will use the default methods but I do know I will need to override the method at least once. Also what other methods should I consider for what I am trying to do? Example of what I am trying to do: I have a set of Objects that act like

问题 Consider following situation: Object > MyClass > MyClassA, MyClassB If I want something in the Object level, for example, I added printDetail(); How can I do it in Java implementation? Moreover, can I override all the Object's method. For example, I need to have a whole new .toString(), can I override it? Thanks. 回答1: No it cannot, not really anyway. Objective C is a dynamically typed and scoped language, which makes it very amenable to features like categories. The closest you can come to

问题 @interface UIViewController (WithAdditionalProperties) @property (nonatomic, copy) void (^someBlock)(); @property (strong, atomic) UIImageView *someView @end It would seem these properties aren't synthesized on UIViewController instances. When I access them in code, I get a NSInvalidArgumentException. But the compiler doesn't complain. What am I doing wrong? 回答1: When you declare a property in a category you do not get the backing variable that you would normally get. You are merely adding a

问题 I am currently implementing local receipt validation following Apple's Receipt Validation Programming Guide . I have defined a category on NSBundle that conforms to SKRequestDelegate and that offers a method for receipt validation, which I call from inside main() before it initializes the application delegate and passes it to UIApplicationMain() . This is what the documentation says: Perform receipt validation immediately after your app is launched, before displaying any user interface or

问题 I'm using categories with Core Data. Some of the tutorials I've read and lectures I've listened to say that categories are often considered "bad" practice. But because Objective-C is so dynamic it seems perfectly okay to define methods somewhere else, especially because only public properties of a class can be used. What are the pitfalls I should be looking out for when using categories? Or is there some reason that categories are actually bad practice? The reason I'm using them with Core

问题 I have a category on UIImage that is written in Objective-C. The following are some example methods. How do I call these methods in Swift? +(UIImage *) imageOrPDFNamed:(NSString *)resourceName; +(UIImage *) imageWithPDFNamed:(NSString *)resourceName; I have tried the following and it does not recognize the methods: let image = UIImage(imageOrPDFNamed:"test.pdf") let image = UIImage(PDFNamed:"test.pdf") 回答1: There are various cases for categories function and it's calling conventions. 1)In

问题 I have a category on UIImage that is written in Objective-C. The following are some example methods. How do I call these methods in Swift? +(UIImage *) imageOrPDFNamed:(NSString *)resourceName; +(UIImage *) imageWithPDFNamed:(NSString *)resourceName; I have tried the following and it does not recognize the methods: let image = UIImage(imageOrPDFNamed:"test.pdf") let image = UIImage(PDFNamed:"test.pdf") 回答1: There are various cases for categories function and it's calling conventions. 1)In

问题 Here is a situation: Hockeyapp and testflight every now and then complain about me "attempting to insert nil object" in mutable dictionaries/arrays. I know the right thing is to check for nil all the time, and I do when it makes sense.. Our testers can not catch those crashes, but AppStore users obviously can. My guess is that sometimes server returns NSNulls when it should not. So not to insert checks for nil everywhere in the huge project my idea was to create a separate target for the

问题 Here is a situation: Hockeyapp and testflight every now and then complain about me "attempting to insert nil object" in mutable dictionaries/arrays. I know the right thing is to check for nil all the time, and I do when it makes sense.. Our testers can not catch those crashes, but AppStore users obviously can. My guess is that sometimes server returns NSNulls when it should not. So not to insert checks for nil everywhere in the huge project my idea was to create a separate target for the