Question

代码中的package main import ( "fmt" "math/rand" "sync" "time" ) type RequestHandler struct { locker sync.Mutex concurrentRequests map[string]*sync.Mutex } func (h *RequestHandler) DoSomething(id string) { // obtain a lock var idLock *sync.Mutex needlock := true for needlock { h.locker.Lock() if h.concurrentRequests == nil { h.concurrentRequests = make(map[string]*sync.Mutex) } idLock = h.concurrentRequests[id] // this is the only way to "acquire a lock": to be the one creating it - otherwise if there already // is a lock we just block until it unlocks and then try again, assuming it will be removed from the // map any moment and we'll get back to this line again and get to create it if idLock == nil { // in this case we are creating the lock, we can safely lock it here without risk of deadlock idLock = &sync.Mutex{} h.concurrentRequests[id] = idLock needlock = false idLock.Lock() h.locker.Unlock() } else { h.locker.Unlock() idLock.Lock() idLock.Unlock() } // then try again if we didn't get a lock } defer func() { // sync access to map h.locker.Lock() h.concurrentRequests[id] = nil // remove this lock from the set h.locker.Unlock() // we're done, let the next guy access this id idLock.Unlock() }() // DO THE WORK HERE fmt.Println(fmt.Sprintf("Starting work on id '%s'...", id)) // hard at work... time.Sleep(time.Duration((rand.Int() % 50)) * time.Millisecond) fmt.Println(fmt.Sprintf("Ending work on id '%s'...", id)) } func main() { reqHandler := &RequestHandler{} for i := 0; i < 1000; i++ { go reqHandler.DoSomething(fmt.Sprintf("%v", rand.Int()%20)) time.Sleep(5 * time.Millisecond) } }工作正常，但在点击时它不会显示检查图标。有什么想法吗？

NSButtonCell

以下是行动代码：

  - (NSCell *)outlineView:(NSOutlineView *)outlineView dataCellForTableColumn:(NSTableColumn *)tableColumn item:(id)item {

        if ([[tableColumn identifier] isEqualToString:@"select"]) {

            NSButtonCell *cell = [[NSButtonCell alloc]init];
            [cell setButtonType:NSSwitchButton];
            [cell setTarget:self];
            [cell setAction:@selector(checkboxChanged:)];
            [cell setTitle:@""];

            return cell;

        } else {
            NSCell *cell = [tableColumn dataCell];
            return cell;  
        }  
    }

Answer 1

我不确定为什么你的第一个解决方案不起作用 - 也许你没有让你的代表联系起来？请注意，数据源和委托是两个不同的东西。

您在答案中实施的方法（数据源）不适合这样做。数据源，尤其是numberOfRowsInTableView:和tableView:objectValueForTableColumn:row:，应仅返回正在呈现的内容，而不是创建视图/单元格对象。

我建议在你的xib中创建和配置NSButtonCell，如果你有一个，或者在你创建表视图及其列的同一个地方 - 这也是设置每个列的单元格的正确位置。

Answer 2

我通过将上述代码从NSOutlineView delegate方法outlineView: dataCellForTableColumn:item:更改为delegate方法outlineView: objectValueForTableColumn: byItem:

来解决了这个问题

像这样：

- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)item {

    if ([[tableColumn identifier] isEqualToString:@"select"])  {

        NSButtonCell* cell = [tableColumn dataCell];
        [cell setSelectable:YES];
        [cell setEnabled:YES];
        [cell setTransparent:NO];
        [cell setButtonType:NSSwitchButton];
        [cell setTarget:self];
        [cell setAction:@selector(checkboxChanged:)];
        [cell setTitle:@""];

        return cell;
    }

    return nil;
}

现在它完美无缺。

NSButtonCell NSSwitchButton不显示复选框

2 个答案: