objective-c-literals

问题 What does it mean when you put an @ before an integer in Objective-C? Like so: @4 回答1: It is the NSNumber literal. A shortcut for this: [NSNumber numberWithInt:4]; 来源： https://stackoverflow.com/questions/17629874/what-does-it-mean-when-you-put-an-before-an-integer-in-objective-c

问题 I read all about the new Objective-C literals, and used Xcode to convert my old code, but the indexing code didn't change. I changed it by hand but then it wouldn't compile. I saw a post that said we have to wait until iOS 6, but I want the indexing NOW! Is there any solution? 回答1: Well, there is a way to do it! Add the indexing methods as a category to NSArray and NSDictionary, and you can get the feature for most of the classes you'd want it for. You can read up on ObjectiveC literals here.

问题 I read all about the new Objective-C literals, and used Xcode to convert my old code, but the indexing code didn't change. I changed it by hand but then it wouldn't compile. I saw a post that said we have to wait until iOS 6, but I want the indexing NOW! Is there any solution? 回答1: Well, there is a way to do it! Add the indexing methods as a category to NSArray and NSDictionary, and you can get the feature for most of the classes you'd want it for. You can read up on ObjectiveC literals here.

问题 It's always been possible to create NSArrays (and NSDictionaries/NSNumber) with vararg method calls, like: [NSArray arrayWithObjects: @"a", @"b", @"c", nil]; Can these be created with in-line literals in a new improvement to LLVM and Clang? 回答1: With this change to the LLVM codebase, Apple has added a new syntax for literals in upcoming versions of the Clang compiler. Before, arrays were created using a C-based array and were converted on the fly into Objective-C objects, such as: NSArray*

问题 It's always been possible to create NSArrays (and NSDictionaries/NSNumber) with vararg method calls, like: [NSArray arrayWithObjects: @"a", @"b", @"c", nil]; Can these be created with in-line literals in a new improvement to LLVM and Clang? 回答1: With this change to the LLVM codebase, Apple has added a new syntax for literals in upcoming versions of the Clang compiler. Before, arrays were created using a C-based array and were converted on the fly into Objective-C objects, such as: NSArray*

问题 This question already has an answer here : Closed 7 years ago . Possible Duplicate: Is literal creation of an NSMutableDictionary less efficient than the class helper method? According to the WWDC video that introduces ObjectiveC literals, NSMutableArray s can be initialized like so: [NSMutableArray arrayWithArray:@[]]; but what if we were to do it like this: [@[] mutableCopy]; I know that one is initializing the array, and the other is just providing a shallow copy; thus the memory

问题 I came across the following: NSArray *array = @[object1, object2]; It seems to be creating an NSArray , but is this array instance an autoreleased object, or must I release it? 回答1: This is a new collection literal available in the compiler that ship with xcode 4.4 and above @[object1, object2]; is equivalent to [NSArray arrayWithObjects:object1, object2, nil]; so yes, it is an autoreleased object, if you need this to be retained, you can do myRetainedArray = [@[object1, object2] retain];

问题 I have this line in Objective-C. NSMutableArray *mutableArray; [mutableArray addObject:@{ @"Something" : aObject, @"Otherthing" : anotherObject }]; What does the @{ ... } part do exactly? It is an object, but it seems to create some kind of key, value pair on the fly. 回答1: It is creating NSDictionary object as you said. Syntax is simple NSDictionary* dictionary = @{key: object, key: object}; In your example, keys are objects of NSString class. It is important to remember that dictionary

问题 There is a literal syntax to add object and change object in an NSMutableDictionary, is there a literal syntax to remove object? 回答1: Yes, but... :-) This is not supported by default, however the new syntax for setting dictionary elements uses the method setObject:forKeyedSubscript: rather than setObject:forKey: . So you can write a category which replaces the former and either sets or removes the element: @implementation NSMutableDictionary (RemoveWithNil) - (void) setObject:(id)obj

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Should I prefer to use literal syntax or constructors for creating dictionaries and arrays? Is there any difference between: NSArray *array = @[@"foo", @"bar"]; and NSArray *array = [NSArray arrayWithObjects:@"foo", @"bar", nil]; Is one of those more stable, faster, or anything else? 回答1: This documentation doesn't mention anything about efficiency directly, but does mention that NSArray *array = @[@"foo", @"bar