程序中有如下代码：
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle:@"Something was done."
message:@"ok"
delegate:self
cancelButtonTitle:@"OK!"
otherButtonTitles:nil];
[alert show];
[alert release];
在xcode环境中 报告错误
error: 'release' is unavailable: not available in automatic reference counting mode [3]
解决办法：
在xcode中选择 project navigator （最左边的视窗）->选中项目名称 ->在主窗口中显示的 project 和targets中选择 project面板->选择building settings-> 在Apple LLVM compiler 3.0 -language 中选择 Ojective-C Automatic Reference couting 选项，把yes 修改成no。
也可以在建立项目的时候不要选择Using Automatic Reference counting 选项。
ARC 是4.2新提供的选项
相关文章可以查看
http://stackoverflow.com/questions/6914453/dealloc-method-gone-from-the-viewcontroller-implementation-file-template-in-xcod
主要意思是
Most likely you have created a project that uses the new ARC (Automatic Reference Counting) and therefore do not need the dealloc method because calling retain or release is no longer allowed when compiling with this option.
所以不需要去手工release了