1.数组，字典，集合等下标越界，或者insert了一个nil对象。

- (void)testArrayOutOfBounds
{
    NSArray *testArray = @[@1,@2,@3];
    
    NSNumber *num = testArray[3];
}

- (void)testDicSetNilValueCrash
{
    // 构造不可变字典时 key和value都不能为空
    NSString *nilValue = nil;
    NSString *nilKey = nil;
    NSDictionary *dic1 = @{@"key" : nilValue};
    NSDictionary *dic2 = @{nilKey : @"value"};
}

- (void)testMutableDicSetNilValueCrash
{
    NSString *value = nil;
    NSMutableDictionary *mDic = [NSMutableDictionary dictionary];
    
    // via Dic set, leading crash
    [mDic setObject:value forKey:@"key"];
    
    // via KVO set, it's safe
    [mDic setValue:value forKey:@"key"];
}

2.调用了一个不存在的方法，而没有实现消息转发

- (void)testUnrecogernizedSelectorCash
{
    [self performSelector:@selector(testSel) withObject:nil afterDelay:0];
}

3.多线程并发导致的。当某个对象会被多个线程修改的时候，有可能一个线程访问这个对象的时候另一个线程已经把它删掉了，导致crash。
解决方法：加锁或者用@synchronized

4.repeat的NSTimer
timer对target持有强引用, 必须确保dealloc前已经invalidate并设为nil, 否则会内存泄漏

5.强引用一个单例会崩溃

6.强引用delegate不知道会不会崩溃？？？

7.tableView

- (void)testTableViewUpdateCrash
{
    NSIndexPath *insertIndexPath = [NSIndexPath indexPathForRow:0 inSection:0];
    NSIndexPath *deleteIndexPath = [NSIndexPath indexPathForRow:1 inSection:0];
    NSIndexPath *reloadIndexPath = [NSIndexPath indexPathForRow:2 inSection:0];
    NSIndexPath *moved1IndexPath = [NSIndexPath indexPathForRow:3 inSection:0];
    NSIndexPath *moved2IndexPath = [NSIndexPath indexPathForRow:4 inSection:0];

    [self.tableView beginUpdates];
    
    [self.tableView insertRowsAtIndexPaths:@[insertIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
    [self.tableView deleteRowsAtIndexPaths:@[deleteIndexPath]withRowAnimation:UITableViewRowAnimationAutomatic];
    [self.tableView reloadRowsAtIndexPaths:@[reloadIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
    [self.tableView moveRowAtIndexPath:moved1IndexPath toIndexPath:moved2IndexPath];
    
    [self.tableView endUpdates];
}