AlertView点击确定后再执行后面的代码-runloop的妙用

- (BOOL)beforeBackButtonClickEvent {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"舍弃流程？" delegate:self cancelButtonTitle:@"否" otherButtonTitles:@"是", nil];
[alert show];
CFRunLoopRun();

return back;
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
//否
if (buttonIndex == 0) {
back = NO;
}
//是
else {
back = YES;
}
CFRunLoopStop(CFRunLoopGetMain());
}