NSAutoreleasePool 和 @autoreleasepool blocks 区别

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////  main.m//  HelloWorld////  Created by Erica Sadun on 4/24/09.//  Copyright __MyCompanyName__ 2009. All rights reserved./** xcode4.3引入ARC，release这块就有些变化，当你使用ARC，就必须将NSAutoreleasePool的地方换成 @autoreleasepool 关于NSAutoreleasePool的解释官方的最清楚 Important If you use Automatic Reference Counting (ARC), you cannot use autorelease pools directly. Instead, you use @autoreleasepool blocks instead. For example, in place of: NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init; // Code benefitting from a local autorelease pool. [pool release]; you would write: @autoreleasepool { // Code benefitting from a local autorelease pool. } @autoreleasepool blocks are more efficient than using an instance of NSAutoreleasePool directly; you can also use them even if you do not use ARC. **/#import <UIKit/UIKit.h>#import "HelloWorldAppDelegate.h"  //如果下面第二个参数直接用nil,不用import这个Delegate.h头文件也可int main(int argc, char *argv[]) {        NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];    NSLog(@"nil如何调用窗口呢");    int retVal = UIApplicationMain(argc, argv, nil,nil); //等效下一句，第二个nil表示就把模板生成的Delegate类作为默认参数        //int retVal = UIApplicationMain(argc, argv, nil,NSStringFromClass([HelloWorldAppDelegate class]));    [pool release];    return retVal;}