objective-c - "Collection NSArray was mutated while being enumerated"仅在 Release模式下

Question

我收到“Collection NSArray was mutated while being enumerated” 异常，仅在 Release模式下。当我在 Debug模式下运行应用程序时，一切正常。

如果 Release模式下的调试器是准确的，它会在这行代码上崩溃:

- (void)initPersonsTableTableColumnMetadata:(CBEditPersonTableColumnMetadata *)metadata count:(NSInteger)valuesCount
{
    personsTableColumnMetadata = [[NSMutableDictionary alloc] initWithCapacity:valuesCount];
    NSAutoreleasePool *metadataPool = [[NSAutoreleasePool alloc] init];
    for (NSUInteger i = 0; i < valuesCount; i++) {
        CBEditPersonTableColumnMetadata aMetadata = metadata[i];
        NSValue *metadataValue = [NSValue valueWithBytes:&aMetadata objCType:@encode(CBTableColumnMetadata)];
        [personsTableColumnMetadata setObject:metadataValue forKey:aMetadata.columnKey];
    }
    FreeAndNil(metadataPool);
}


-(CBEditPersonTableColumnMetadata)tableColumnMetadataForKey:(NSString *)aKey
{
    CBEditPersonTableColumnMetadata theMetadata;
    NSValue *storedValue = [personsTableColumnMetadata valueForKey:aKey];
    if (storedValue) {
        [storedValue getValue:&theMetadata]; //here
        return theMetadata;
    }
}

- (void)addColumnsToPersonTable:(CBEditableTableView *)table withKeys:(NSArray *)keys andAutosaveName:(NSString*)autosaveName
{
    for (NSString *columnKey in keys) {
        CBEditPersonTableColumnMetadata metadata = [self tableColumnMetadataForKey:columnKey];
        NSTableColumn *newColumn = [[NSTableColumn alloc] initWithIdentifier:columnKey];

        NSCell *cell = nil;

        if ([metadata.columnKey isEqualToString:@"Dragging"]) {
            cell = [[NSImageCell alloc] init];

        } else if ([metadata.editType isEqualToString:[self editableButton]]) {
            cell = [[NSButtonCell alloc] init];
            [cell setAction:@selector(selectAndOpenEditLookup:)];
            [cell setTag:[metadata.editEntity intValue]];
            [cell setImage:[NSImage imageNamed:@"edit-inlist-16x16.png"]];
            [(NSButtonCell*)cell setImageScaling:NSImageScaleProportionallyDown];
            [cell setTarget:self];
            [cell setTitle:@""];

        } else {
            cell = [[CBPaddedTextCell alloc] init];
            if ([metadata.editType isEqualToString:[self notEditableComboBox]]) {
                [cell setEditable:NO];
            }
        }

        [newColumn setResizingMask:NSTableColumnUserResizingMask];
        [[newColumn headerCell] setStringValue:[NSString stringWithFormat:@"  %@",metadata.columnHeader]];

        [[newColumn headerCell] setLineBreakMode:NSLineBreakByTruncatingTail]; // or NSLineBreakByTruncatingMiddle

        if (metadata.minWidth > 0.0) {
            [newColumn setMinWidth:metadata.minWidth];
        }
        if (metadata.maxWidth > 0.0) {
            [newColumn setMaxWidth:metadata.maxWidth];
        }

        [newColumn setWidth:100.0];

        if (![metadata.editType length])
            if ([cell isKindOfClass:[NSTextFieldCell class]])
                [(NSTextFieldCell*)cell setTextColor:[NSColor grayColor]];

        [newColumn setDataCell:cell];
        FreeAndNil(cell);

        if (![metadata.editType isEqualToString:[self editableButton]]) {
            NSDictionary *bindingOptions =  [NSDictionary dictionaryWithObjectsAndKeys:
                                            [NSNumber numberWithBool:NO], NSCreatesSortDescriptorBindingOption,
                                            [NSNumber numberWithBool:YES], NSEditableBinding,
                                            nil];

            [newColumn bind:@"value" toObject:[table arrayController] withKeyPath:[NSString stringWithFormat:@"arrangedObjects.%@", metadata.bindingKeyPath] options:bindingOptions];
            [[newColumn dataCell] setEditable:YES];
        }

        [newColumn setIdentifier:columnKey];
        [table addTableColumn:newColumn];
        FreeAndNil(newColumn);
    }

    NSTableColumn *newColumn = [[NSTableColumn alloc] initWithIdentifier:@"Remove"];

    NSButtonCell *cell = [[NSButtonCell alloc] init];
    [cell setAction:@selector(removeEditableItem:)];
    [cell setImage:[NSImage imageNamed:@"remove.png"]];
    [cell setImageScaling:NSImageScaleProportionallyDown];
    [cell setTarget:self];
    [cell setTitle:@""];
    [newColumn setMinWidth:20];
    [newColumn setMaxWidth:20];
    [newColumn setWidth:20.0];
    [[newColumn headerCell] setStringValue:@""];

    [newColumn setDataCell:cell];
    FreeAndNil(cell);
    [table addTableColumn:newColumn];
    FreeAndNil(newColumn);

    [table setNeedsDisplay];
    [table reloadData];

    [table setAutosaveName:autosaveName];
    [table setAutosaveTableColumns:YES];
}

- (void)windowDidLoad
{
    [super windowDidLoad];


    NSArray * artistKeys = [NSArray arrayWithObjects:@"Dragging", @"DisplayName", @"FirstName", @"LastName", @"SortName", @"ID", nil];
    [editableArtistTable setArrayController:artistsArrayController];
    [self addColumnsToPersonTable:editableArtistTable withKeys:artistKeys andAutosaveName:@"editableArtistTable"];

CBEditPersonTableColumn元数据

typedef struct _CBEditPersonTableColumnMetadata {
    NSString *columnKey;
    NSString *columnHeader;
    NSString *bindingKeyPath;
    CGFloat minWidth;
    CGFloat maxWidth;
    NSString *editType;
    NSString *editEntity;
    BOOL     forbidEmpty;
} CBEditPersonTableColumnMetadata;

不知道为什么。 Debug模式一切正常。

更新:控制台日志:

2014-12-17 16:13:20.580 *** Collection <__NSArrayI: 0xf60f0a0> was mutated while being enumerated.
2014-12-17 16:13:20.582 Colr (
    0   CoreFoundation                      0x9711a343 __raiseError + 195
    1   libobjc.A.dylib                     0x98bbda2a objc_exception_throw + 276
    2   CoreFoundation                      0x97119c0a __NSFastEnumerationMutationHandler + 362
    3   Colr                     0x00165e16 -[CBEditItemWithOutletsBase addColumnsToPersonTable:withKeys:andAutosaveName:] + 149
    4   Colr                     0x00192413 -[CBEditItemWithOutlets windowDidLoad] + 343

Answer 1

好吧，经过一番调查(您可以看到上面的评论)，结果发现问题出在 initPersonsTableTableColumnMetadata:count: 方法

下面一行:

NSValue *metadataValue = [NSValue valueWithBytes:&aMetadata objCType:@encode(CBTableColumnMetadata)];  

应该是:

NSValue *metadataValue = [NSValue valueWithBytes:&aMetadata objCType:@encode(CBEditPersonTableColumnMetadata)];  

@encode 结构类型不正确。
因此，当尝试将其解码回 CBEditPersonTableColumnMetadata 结构时，它崩溃了。

我仍然有点困惑为什么异常表明这是由于在枚举数组时改变数组造成的，但是崩溃的方法是从枚举内部调用的(即使它对数组的对象没有影响) )，并修复上述问题解决了崩溃问题。