Databases
StackOverflow2013
Postsdbo
POunexplained behavioural difference between objectWithID: versus existingObjectWithID:
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POunexplained behavioural difference between objectWithID: versus existingObjectWithID:
    primarykey
    data
    text
    <p>I understand the documented differences between these two calls. However does anyone know the reasons for the following observed behaviour I have noticed:</p> <p>If I have a parentContext and a temporary childContext where I use the childContext to edit, insert and deleted objects, if use [childContext objectWithID:objectID]; to retrieve a known existing managed object, present in the parent context, it will sometimes give me an object with a fault that on being fired fails and generates an exception. I understand objectWithID: will, by design, always return an object in a faulted state regardless of if an actual managedObject exists for the given objectID. However if the object actually exists in the parent context, I would expect that when any of the properties are accessed, the object will always be successfully retrieved from the parent context (e.g. the fault will be fired) without any problem. If I use [childContext existingObjectWithID:objectID]; I find it does indeed always succeed. </p> <p>For the record, I have turned off caching on the child context and this same behaviour occurs after [childContext resetContext] has been called - so it's not an artefact of old cached data hanging around that is inconsistent with the parent context. </p> <p>The documentation alone seems to me to be insufficient to explain this behaviour. I can of course chalk it up to experience and just say "I now know to always use existingObjectWithID: when passing object IDs to my child edit context perform block" but I feel uneasy and would like to understand exactly what is going on here (not least so I can understand if there is any performance impact of using the one as over the other but also to understand what the constraint is so I can ensure there isn't some bad practice I'm unnecessarily implementing in my code and then using a wrong or inefficient call to fix it).</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USTheBasicMind
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POunexplained behavioural difference between objectWithID: versus existingObjectWithID:
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POunexplained behavioural difference between objectWithID: versus existingObjectWithID:
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POunexplained behavioural difference between objectWithID: versus existingObjectWithID:
      1. USHeikoG
      1. VTFavorite
    1. This table or related slice is empty.
 

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