这种方法中的内存泄漏在哪里？

Question

我无法在此排序方法中找到内存泄漏，启用了ARC。我尝试使用NSDate对象数组准备一个更简单的示例，但那个行为正常。这段代码的问题在哪里？感谢。

- (void)sortDataSourceByDateNewestFirst:(BOOL)newestFirst
{
    NSArray *sortedResponseEntities;
    NSArray *sortedResponseObjects;

    if (newestFirst) {
        // sort responseEntities
        sortedResponseEntities = [self.responseEntitiesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
            return [responseEntity2.date compare:responseEntity1.date];
        }];

        // sort responseObjects
        sortedResponseObjects = [self.responsesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
            return [response2.dateUp compare:response1.dateUp];
        }];
    } else {
        // sort responseEntities
        sortedResponseEntities = [self.responseEntitiesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
            return [responseEntity1.date compare:responseEntity2.date];
        }];

        // sort responseObjects
        sortedResponseObjects = [self.responsesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
            return [response1.dateUp compare:response2.dateUp];
        }];
    }
    self.responseEntitiesObjects = [sortedResponseEntities mutableCopy];
    self.responsesObjects = [sortedResponseObjects mutableCopy];
}

编辑，这是Instruments的输出：

Answer 1

为什么要复制数组而不是简单地将其分配给属性？无论如何，在您发布的代码中没有可见的泄漏，因此案例是：

1）内存尚未被释放，因为设备仍然不需要它，内存被标记为可重用，并将在事件循环的下一次迭代中释放。如果是这种情况，只需将代码包装在autoreleasepool中就可以了：

- (void)sortDataSourceByDateNewestFirst:(BOOL)newestFirst
{
    @autoreleasepool {

        NSArray *sortedResponseEntities;
        NSArray *sortedResponseObjects;

        if (newestFirst) {
            // sort responseEntities
            sortedResponseEntities = [self.responseEntitiesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
                return [responseEntity2.date compare:responseEntity1.date];
            }];

            // sort responseObjects
            sortedResponseObjects = [self.responsesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
                return [response2.dateUp compare:response1.dateUp];
            }];
        } else {
            // sort responseEntities
            sortedResponseEntities = [self.responseEntitiesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
                return [responseEntity1.date compare:responseEntity2.date];
            }];

            // sort responseObjects
            sortedResponseObjects = [self.responsesObjects sortedArrayUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
                return [response1.dateUp compare:response2.dateUp];
            }];
        }
        self.responseEntitiesObjects = [sortedResponseEntities mutableCopy];
        self.responsesObjects = [sortedResponseObjects mutableCopy];
    }
}

2）您对数组持有的对象保持强引用。在这种情况下，即使在释放数组之后（当覆盖属性时由ARC自动地），仍然具有保留计数＆gt; = 1的所保持的对象不能被释放，因此不释放存储器。如果你不再持有对引用它们的对象的引用，那么你就会泄漏并且对象现在是僵尸（你将通过运行Leaks Instrument来看到它们）。

3）如果持有的对象是自定义对象，那么泄漏就像你采用NSCopying协议一样，在这种情况下你应该发布对象实现（至少是相关的方法）

编辑：刚刚注意到您的属性是NSMutableArray，您可以将其更改为：

- (void)sortDataSourceByDateNewestFirst:(BOOL)newestFirst
{
    //@autoreleasepool {

        if (newestFirst) {
            // sort responseEntities
            [self.responseEntitiesObjects sortUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
                return [responseEntity2.date compare:responseEntity1.date];
            }];

            // sort responseObjects
            [self.responsesObjects sortUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
                return [response2.dateUp compare:response1.dateUp];
            }];
        } else {
            // sort responseEntities
            [self.responseEntitiesObjects sortUsingComparator:^NSComparisonResult(ResponsesEntityObject *responseEntity1, ResponsesEntityObject *responseEntity2) {
                return [responseEntity1.date compare:responseEntity2.date];
            }];

            // sort responseObjects
            [self.responsesObjects sortUsingComparator:^NSComparisonResult(ResponsesObject *response1, ResponsesObject *response2) {
                return [response1.dateUp compare:response2.dateUp];
            }];
        }
    //}
}

通过这种方式，您无需复制数组，只需对现有数组进行重新排序即可。无论如何，这不会解决你的问题，因为正如我所说，这里没有明显的泄漏。

你应该运行仪器来查明泄漏是否和在哪里。