verify input parameter of init method and return nil before invoke [super init]
Hi All,
if below code valid ? All sample codes I could find invoke self = [super
init] first and then check the input parameter inside if (self) block.
@implementaion Bla
- (id)initWithFoo:(NSString *)foo
{
if (foo == nil) {
return nil;
}
self = [super init];
if (self) {
_foo = foo;
.
}
return self;
}
I had thought there would be memory leak. Bla * b = [Bla alloc ]
initWithFoo:nil]; . However under ARC using Instruments Leaks, there are no
leak found.
Thanks in advance!
Bob Cromwell
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Re: Questions about CoreData and object graphs
Actually your guess is wrong. Core Data could handle this by turn the object to fault. Have a look at the method refreshObject:mergeChanges. Bob Cromwell On 2012-11-15, at 上午10:30, William Squires wrote: 1) Can CoreData properly manage an object graph where the objects form a circular reference (i.e.) Entity Node int nodeType Node onTopOf // 1:1 relationship to another Node entity Node under // another 1:1 relationship End This would be a doubly-linked list in a circular queue so that you could go either direction from any Node entity. My guess is… no. 2) Without CoreData, if I simply declare in my model classes that they implement NSCoding (and I implement all the initWithCoder: and encodeWithCoder: methods), will this properly handle such a situation (i.e. a possibly circular object graph)? ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/bob.cromwell2012%40gmail.com This email sent to bob.cromwell2...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Core Data : Batch Faulting while take advantage of cache
Hi there,
In Core Data Programming Guide Apple recommend a way to batch fire fault a
collection of objects, It should be implemented as below:
NSArray * arrayOfFaults = [NSArray arrayWithObjects:object1,object2,nil];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@self IN %@,
arrayOfFaults];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]
initWithEntityName:@Foo];
[fetchRequest setPredicate:predicate];
[fetchRequest setReturnsObjectsAsFaults:NO];
[managedObjectContext executeFetchRequest:fetchRequest error:NULL];
However using Core Data Instrument on iOS 6 simulator, I found this fetch
almost as same time as other fetch. In other words, it goes to disk and did not
use the cache. It's unreasonable . Since it's an IN clause , Core Data
could use the objectID to find object in cache. There are no need to go to the
disk if all of them could be found in cache.
I am pretty sure these objects in arrayOfFaults are in cache. If I replace
above code with this one, not cache miss are reported:
for (NSManagedObject *object in arrayOfFaults){
[object willAccessValueForKey:nil];
}
So my question is : are there any way to batch fault objects while take
advantage of the cache ?
Bob Cromwell
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Re: Core Data fetch performance
Hi Hunter, I am very interested in what bugs they fixed. Could you please share more about it , e.g. an official bug fix report ? Thanks Bob The API changes came in iOS 5 but in iOS 6 they fixed enough bugs to make it work right. :-) On Nov 11, 2012, at 4:50 PM, Rick Mann rm...@latencyzero.com wrote: GCD, along with the Core Data changes in iOS 5 and 6 for handling concurrency, make this much easier than it used to be (or at least cleaner and harder to screw up as badly). By the way, what were the changes in iOS 6? I can't find specific Core Data notes for iOS 6, only iOS 5. Thanks! ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/bob.cromwell2012%40gmail.com This email sent to bob.cromwell2...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: ARC issue
According to ARC documentation, out parameter will be changed to auto release
one:
NSError ** error will be auto changed to NSError * __autorelease * error.
So It's expected behavior that crash happens. An article about this here
http://blog.pioneeringsoftware.co.uk/2012/03/06/out-parameters-when-arcing
On 2012-11-7, at 下午9:05, Andreas Grosam wrote:
Xcode 4.5.1, ARC enabled.
I've this C++ member function, for a testing environment (gtest):
NSDictionary* fetchUser(NSNumber* ID, NSError** error)
{
id user = nil;
//@autoreleasepool // crashes when @autoreleasepool is enabled
{
id data = ...; // response body of a HTTP Response (NSData) or NSError
object, never nil.
if ([data isKindOfClass:[NSData class]]) {
user = [NSJSONSerialization JSONObjectWithData:data
options:0
error:error];
}
else if (error) {
*error = data;
}
} // autoreleasepool
return user;
}
The problem here is, if the autorelease pool is **enabled**, I get a crash in
the caller's code:
NSError* err = nil;
NSDictionary* deletedUser = this-fetchUser(userID, err);
EXPECT_TRUE(deletedUser == nil);== the crash occurs
**before** this statement, but **after** the return statement of the function
fetch user.
The debugger does not show a stack frame to confirm this, though.
libobjc.A.dylib`objc_msgSend:
0x7fff86b2fe80: testq %rdi, %rdi
0x7fff86b2fe83: je 0x7fff86b2feb0; objc_msgSend + 48
0x7fff86b2fe85: testb $1, %dil
0x7fff86b2fe89: jne0x7fff86b2fec7; objc_msgSend + 71
0x7fff86b2fe8c: movq (%rdi), %r11
0x7fff86b2fe8f: pushq %rax
== 0x7fff86b2fe90: movq 16(%r11), %r10 // Thread 1:
EXC_BAD_ACCESS (code=13, address=0x0)
0x7fff86b2fe94: movl %esi, %eax
0x7fff86b2fe96: andl (%r10), %eax
0x7fff86b2fe99: movq 16(%r10,%rax,8), %r11
0x7fff86b2fe9e: incl %eax
0x7fff86b2fea0: testq %r11, %r11
0x7fff86b2fea3: je 0x7fff86b2fedb; objc_msgSend + 91
...
There is no stack frame.
This has something to do with the error parameter. If I pass nil for the
error parameter, the crash does not occur anymore.
Any hints?
Thanks in advance!
Andreas
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