Databases
StackOverflow2013
Postsdbo
POHow to efficiently get all instances from deeper level in Cocoa model?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow to efficiently get all instances from deeper level in Cocoa model?
    primarykey
    data
    text
    <p>In my Cocoa Mac app I have an instance <code>A</code> which contains an unordered set of instances <code>B</code> which in turn has an ordered set of instances <code>C</code>. An instance of <code>C</code> can only be in one instance <code>B</code> and <code>B</code> only in one <code>A</code>.  </p> <p>I would like to have an unordered set of all instances <code>C</code> available on instance <code>A</code>. I could enumerate over all instances <code>B</code> each time, but that seems expensive for something I need to do often. However, I am a bit worried that keeping track of instances <code>C</code> in <code>A</code> could become cumbersome and be the cause of  inconsistencies, for example if an instance <code>C</code> gets removed from <code>B</code> but not from <code>A</code>. </p> <p><em>Solution 1</em> – Use a <code>NSMutableSet</code> in <code>A</code> and add or remove <code>C</code> instances whenever I do the same operation in <code>B</code>. </p> <p><em>Solution 2</em> – Use a weak referenced <code>NSHashTable</code> in <code>A</code>. When deleting a <code>C</code> from <code>B</code> it should disappear for <code>A</code> as well. </p> <p><em>Solution 3</em> – Use key value observing in <code>A</code> to keep track of changes in <code>B</code>, and update a <code>NSMutableSet</code> in <code>A</code> accordingly. </p> <p><em>Solution 4</em> – Simply iterate over all instances <code>B</code> to create the set whenever I need it.  </p> <p>Which way is best? Are there any other approaches that I missed? </p> <p>NB I don't and won't use CoreData for this app. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USJohan Kool
    1. USJohan Kool
    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. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow to efficiently get all instances from deeper level in Cocoa model?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COHave you profiled your code? Do you know that this is where you spend a lot of time? You should probably do profiling before attempting to optimize.
      singulars
      1. POHow to efficiently get all instances from deeper level in Cocoa model?
      1. USMichael Aaron Safyan
    2. COam I take it right all, instances of C are unique among all data?
      singulars
      1. POHow to efficiently get all instances from deeper level in Cocoa model?
      1. USVladimir
    3. CONo, this code I have not profiled yet, mostly because I am still designing it and there is much to profile just yet. It seemed a common enough problem though to ask how others have implemented this. Yes, all instances of `C` are unique. Sorry if that wasn't clear. It should follow logically from `C` being only in one `B`.
      singulars
      1. POHow to efficiently get all instances from deeper level in Cocoa model?
      1. USJohan Kool
 

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