nsmutablearray

用途 多线程访问可变变量时，是非线程安全的。可能导致程序崩溃。此时，可以通过使用信号量（semaphore）技术，保证多线程处理某段代码时，后面线程等待前面线程执行，保证了多线程的安全性。使用方法记两个就行了，一个是wait（dispatch_semaphore_wait），一个是signal（dispatch_semaphore_signal）。根据dispatch_semaphore_wait的参数类型提示去创建信号量（dispatch_semaphore_t）即可。 感觉原理跟PV操作如出一辙。 不用semaphore时code: #import <Foundation/Foundation.h> int main(int argc, const char * argv[]) { @autoreleasepool { // insert code here... NSLog(@"Hello, World!"); NSMutableArray *lArrM = [NSMutableArray array]; for (int i = 0; i < 100; ++i) { dispatch_async(dispatch_get_global_queue(0, 0), ^{ [lArrM addObject:@(i)]; }); } } return 0; } 运行结果

I want to sort an NSMutableArray alphabetically. You can do this to sort NSMutableArray: [yourArray sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)]; The other answers provided here mention using @selector(localizedCaseInsensitiveCompare:) This works great for an array of NSString, however the OP commented that the array contains objects and that sorting should be done according to object.name property. In this case you should do this: NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES]; [yourArray sortUsingDescriptors:[NSArray arrayWithObject

I want to add an NSMutableArray of NSStrings to one of my Entities in my core data model. The problem is that this isn't a supported type in Core Data. I tried making a tranformable attribute, but the problem is that I see no way of turning a NSMutableArray to NSData, and then going from NSData, back to an NSMutableArray. Does anyone have an idea as to how this issue can be solved? (I know I can archive the array, but I don't want to do that, I want it to be present in my model). jbrennan You could have a binary data attribute in your modeled object, archive the array to data, and hand it off

I recently started working with UIActivity to share my app to the world, but I have few problems. First, I didn't find how to set the subject of my email. Is there any way? Second, when I set the body text of my email, there is a extra "enter" (first line of the email is blank and my text starts at the second line). Here's the code: NSMutableArray *array = [[NSMutableArray alloc] initWithObjects: @"Test", nil]; UIActivityViewController *activityViewController = [[UIActivityViewController alloc] initWithActivityItems:array applicationActivities:nil]; And in the email, it shows that: " Test "

I know that I can "subclass" an NSMutableArray using "category extensions," i.e. @interface NSMutableArray (MyExtension) , to add new functions to the class. However, is there a way using category extensions to also add new properties to the extension? Note that @interface NSMutableArray (MyStuff) is a category and not a class extension . They are similar in this context, but actually do have quite a few different details. You can't add storage to an existing class through either mechanism. You can use Associative References to associate data with an instance, though. As you said, categories