cocoa-design-patterns

问题 I'm pretty new to iOS development (my first app) and I faced this issue. I have an iPhone app that should get user's current location in multiple ViewControllers upon user button touch. To prevent redundant code (implementing locationManager:didFailWithError , locationManager:didUpdateToLocation:fromLocation , etc. multiple times in different view controllers) I decided to create a custom class called LocationManager : LocationManager.h @interface LocationManager : NSObject

问题 This seems like a typical problem, but I have a UITableView that has identical behavior for two separate data sources. What is the best way of going about designing the class hierarchy to have as little duplication and if/else conditions? The view controller is going to do the same exact thing to both data sources, they're just unique in their data set. Should I have the parent controller just set its data source/respective title? The same issue is relevant as well when using a

问题 I have a dictionary of objects; they are all POCO objects that should be serializable. What technique should I look at for writing these to disk. I'm looking for the simplest option to write a few lists to save state. I think I have 3 options. plist files. However this seems to be limited to only storing predefined objects (strings, numbers etc) not objects (like a person with a name and age). CoreData. (New in 3.0) This would work well; however my data model would need to change to make this

问题 Is there some purpose for this convention? 回答1: Apple likes to use underscores to mean "private", according to the Coding Guidelines for Cocoa: Avoid the use of the underscore character as a prefix meaning private, especially in methods. Apple reserves the use of this convention. Use by third parties could result in name-space collisions; they might unwittingly override an existing private method with one of their own, with disastrous consequences. Method names beginning with underscores are

问题 I am facing a very regular scenario. I have an NSArray which has object of a custom type, say Person. The Person class has the attributes: firstName, lastName and age. How can I get an NSArray containing only one attribute from the NSArray having Person objects? Something like: NSArray *people; NSArray *firstNames = [people getArrayOfAttribute:@"firstName" andType:Person.Class] I have a solution of writing a for loop and fill in the firstNames array but I don't want to do that. 回答1: NSArray

问题 I have an NSArrayController, companiesController bound to a top level Core Data entity, Companies . A Company has many Department 's, and a Department has many Employee ; these are represented by the 1-to-many relationships, departments and employees . Based on the attribute salary of an Employee I thought I could dynamically do this for filtering based on salary inside a UI-called method: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY departments.employees.salary < %@",

问题 I was reading that NSArray is just such a thing. Sounds heavy. I have 7 really fat books here on my desk about Objective-C, Cocoa and C. None of them mention Class Cluster at all, at least I can't find it in the Index at the back of the books. So what's that? 回答1: From Apple's docs.... In short it's a design pattern used in the Foundation framework, which is probably why it's not mentioned in ObjC books. A class cluster is an architecture that groups a number of private, concrete subclasses

问题 Why do some objects not need to be initialized before use in objective-c? For example why is this NSDate *today = [NSDate date]; legal? 回答1: They are initialized within the date method. This is a common way to create autoreleased objects in Objective-C. Allocators of that form are called convenience allocators. To learn more about that, read the "Factory Methods" paragraph in Apple's Cocoa Core Competencies document about Object Creation: http://developer.apple.com/library/mac/#documentation

问题 I'm going through a refactoring and reorganization of my application at the moment. I've realized that some of the separation between models and views, and their controllers has diminished and I wish to do some cleaning up. I have several key classes used in my app: NSPersistentDocument, NSWindowController, and a model class. The NSPersistentDocument class acts as a "model-controller"; it owns an instance of the model class, and manages all interactions with the model. The NSWindowController

问题 I'm creating an iOS application with lots of custom views, so, using default Cocoa views was not an option. Then, I decided to go with the Coordinating / Mediator Controller design patter (learned in Apress - Pro Objective-C Design Patterns for iOS). From the delegate, I create a rootViewController pointing to the view in my coordinating controller: self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; coordinatingController = [C6CoordinatingController sharedInstance]