Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>This issue is discussed at some length in <a href="https://bugzilla.xamarin.com/show_bug.cgi?id=1086" rel="nofollow">Bug 1086</a></p> <blockquote> <p>Well, this is a ref-counting/ownership problem:</p> <p>You create a new MyObject instance in your MyDataSource.GetObjectValue(), then return it to native code, without keeping a reference to it. After returning, you do not own that object anymore, but the managed garbage collector does not know that.</p> <p>Simply store the objects in a list, like this:</p> <pre><code>List&lt;MyObject&gt; list; public MyDataSource () { list = new List&lt;MyObject&gt; (); for (int i = 0; i &lt; 10; i++) { list.Add (new MyObject { Text = "My Row " + i }); } } public override NSObject GetObjectValue (NSTableView tableView, NSTableColumn tableColumn, int row) { return list [row]; } public override int GetRowCount (NSTableView tableView) { return list.Count; } </code></pre> <p>However, this does not solve your copyWithZone: problem. Here, storing the cloned objects locally is not an option, this would leak a lot of memory quickly. Instead, you need to call retain on the cloned object. Unfortunately, NSObject.Retain() is internal in MonoMac.dll, but you can just simply do it like this:</p> <pre><code>static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public NSObject CopyWithZone (IntPtr zone) { var cloned = new MyObject { Text = this.Text }; Messaging.void_objc_msgSend (cloned.Handle, selRetain); return cloned; } </code></pre> </blockquote> <p>From memory the code in the last example isn't complete, you have to combine the two examples and track the new <code>MyObject</code> in a list (or some other collection) as well.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow to implement Cocoa copyWithZone on derived object in MonoMac C#?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USta.speot.is
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThe second code block alone seems to be fixing my problem in practice, but I don't understand your last comment. Is retain not sufficient alone? And if I did store objects in a list somewhere, how would the references ever be released? These objects are being cloned in the bowels of Cocoa where I'll mostly never see them.
      singulars
      1. PO
      1. USJustin Aquadro
    2. COI believe (and my understanding of this is not that great) that any reference to a managed object you return to the native runtime must have at least one reference to it in your application. Otherwise the GC will think the object is ripe for the taking. When the object reference comes back into Mono, it refers to an object that doesn't exist anymore and boom!
      singulars
      1. PO
      1. USta.speot.is
    3. COIs the unmanaged code that's calling the copy method guaranteed to also call Dispose on the copied object (via destroy or dealloc or whatever)? That's the only place I can think of to reliably clean up a global object reference pool.
      singulars
      1. PO
      1. USJustin Aquadro
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload