13

我有NSPointerArray一些NSObject已经被释放的弱点。在调用之前compact我看到的是：

(lldb) po [currentArray count]
1
(lldb) po [currentArray pointerAtIndex:0]
<nil>
(lldb) po [currentArray allObjects]
<__NSArrayM 0x16f04f00>(

)

这是有道理的，但真正奇怪的是，当我调用compact该数组时，我看到了相同的值！Count 仍然返回 1 并且pointerAtIndex:0is nil。

为什么 nil 没有被删除？

编辑

这是完整的代码（是的，它是 XCTesting 框架）：

- (void)testCompaction {
    __weak id testingPointer = nil;

    NSPointerArray *weakArray = [NSPointerArray weakObjectsPointerArray];

    @autoreleasepool {

        NSObject *someObj = [[NSObject alloc] init];

        testingPointer = someObj;

        [weakArray addPointer:(__bridge void*)testingPointer];

        NSLog(@"before compaction inside autorelease: testingPointer = %@ count = %d, allObjects = %@, pointerAtIndex:0 = %@, pointerAtIndex:0 class = %@", testingPointer, [weakArray count], [weakArray allObjects], [weakArray pointerAtIndex:0], [(id)[weakArray pointerAtIndex:0] class]);

        someObj = nil;
    }

    NSLog(@"before compaction outside autorelease: testingPointer = %@ count = %d, allObjects = %@, pointerAtIndex:0 = %@, pointerAtIndex:0 class = %@", testingPointer, [weakArray count], [weakArray allObjects], [weakArray pointerAtIndex:0], [(id)[weakArray pointerAtIndex:0] class]);

    [weakArray compact];

    NSLog(@"after compaction outside autorelease: testingPointer = %@ count = %d, allObjects = %@, pointerAtIndex:0 = %@, pointerAtIndex:0 class = %@", testingPointer, [weakArray count], [weakArray allObjects], [weakArray pointerAtIndex:0], [(id)[weakArray pointerAtIndex:0] class]);
}

和日志：

  before compaction inside autorelease: testingPointer = <NSObject: 0x7de7ff80> count = 1, allObjects = (
    "<NSObject: 0x7de7ff80>"
), pointerAtIndex:0 = <NSObject: 0x7de7ff80>, pointerAtIndex:0 class = NSObject
2015-07-20 14:27:14.062 AppetizeSuite copy[54144:9019054] before compaction outside autorelease: testingPointer = (null) count = 1, allObjects = (
), pointerAtIndex:0 = (null), pointerAtIndex:0 class = (null)
2015-07-20 14:27:22.615 AppetizeSuite copy[54144:9019054] after compaction outside autorelease: testingPointer = (null) count = 1, allObjects = (
), pointerAtIndex:0 = (null), pointerAtIndex:0 class = (null)

为什么compact方法不删除第一个指针？这显然是一个nilbefore call compact。

4

3 回答 3

21

发生这种情况的原因是-compact首先检查是否设置了内部标志“needsCompaction”。如果不是，它只是提早保释。唯一设置标志的情况是通过公共接口将 nil 指针直接插入到数组中。如果在将指针插入数组后释放弱引用对象（并且指针为 nil'd），则不会设置它。

解决此问题的一种方法是在调用-compact. 不理想，但它会工作。

[pa addPointer:nil]; // forces the pointer array to do compaction next time
[pa compact];
于 2016-10-27T00:58:04.197 回答
4

我见过同样的行为。这是一个开放的雷达错误报告： http ://www.openradar.me/15396578

于 2015-07-27T14:55:37.197 回答
0

已经有几年了，使用示例代码显示没有变化。

但是，当使用方法 -replacePointerAtIndex:withPointer 执行指针更新时，-compact 非常有效：

在上面的代码中，替换

someObj = nil;

经过

 [weakArray replacePointerAtIndex:0 withPointer:nil];

之后提供预期的结果[weakArray compact];，代码将在最后一个 NSLog 崩溃

于 2020-05-31T11:14:58.500 回答