What is __NSArrayI and __NSArrayM?
__NSArrayI(or M) cause "unrecognized selector" error.
How to convert to NSArray?
I did test to parse json, twitter api.
http://api.twitter.com/1/followers/ids.json?cursor=-1&screen_name=twitterapi
==> works fine. parsed object is NSCFDictionary class.
(This dictionary contains __NSArrayM class)
http://api.twitter.com/1/statuses/user_timeline.json?&screen_name=twitterapi
==> error. parsed object is __NSArrayM class.
__NSArrayI is a code-word for an immutable array - that is, a "regular" NSArray which you cannot change.
__NSArrayM is a code-word for a mutable array - that is, NSMutableArray. In NSMutableArray, you can add and remove items.
These are classes of the private api. There is a project where you can see all classes of the private api. You are not allowed to use them inside an app for the app store but sometimes it is useful too see how to access the objects and also what kind of object it is. They cannot be converted. I think, getting these kind of objects inside the debugger is just the representation of internal classes, for the classes you are using inside your project. Knowing what kind of class it is, lets you also understand where to look for the problem inside your code.
Here you can see a short lookup of both:
__NSArrayI
__NSArrayM
It is private classes. You shouldn't want to access them or moreover convert them.
If I'm not mistaken NSArray is subclass of _NSArray.
If you are adding/removing some objects to/from your array check that it is of mutable type : NSMutableArray
Related
I dont know how to declare a array which just stores pointers to objects. As per My understanding ,if I use method
[ someArray addObject:someObject ] ,
It would then add the copy of object to array and any changes to object wont get reflected to original object.
What I want is that create a array of pointers which would just point to objects and changes made to objects would persist. pardon me, If I am missing something basic.
An NSArray or NSMutableArray is an array of pointers. No copying is done.
you have your basics wrong. technically when you do that you create the array of pointers to those objects.
http://developer.apple.com/library/ios/#DOCUMENTATION/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html read the description.
If you want to get the object copied you have to explicitly say so.
Look at this question for example
Deep copying an NSArray
By the way you should use an NSMutableArray.
Also look at the superclass NSArray
http://developer.apple.com/library/ios/#DOCUMENTATION/Cocoa/Reference/Foundation/Classes/NSArray_Class/NSArray.html#//apple_ref/occ/cl/NSArray
specifically for the initWithArray:copyItems:
flag
If YES, each object in array receives a copyWithZone: message to
create a copy of the object—objects must conform to the NSCopying
protocol. In a managed memory environment, this is instead of the
retain message the object would otherwise receive. The object copy is
then added to the returned array.
If NO, then in a managed memory environment each object in array simply receives a retain message when it is added to the returned
array.
By default adding an object to a nsmutablearray increases its capacity if necessary, adds a retain for the object, and the pointer to the object.
...if I use method
[ someArray addObject:someObject ] ,
It would then add the copy of object to array and any changes to
object wont get reflected to original object.
While it technically doesn't pertain to the question, I simply must correct your terminology. "Copy" in Objective-C implies that the method -copy is sent to the object, which would create a new object in of itself. What Arrays do is send -retain to their objects, which means that the array itself now owns a stake in the object, which is why changes that don't reference the array (-objectAtIndex:), or have a valid claim to the object itself are not reflected.
What I want is that create a array of pointers which would just point
to objects and changes made to objects would persist. pardon me, If I
am missing something basic.
Well, unfortunately iOS does not support the class NSPointerArray, which would make your life significantly easy in regards to an actual array of pointers. Without getting into any C-craziness, I can only reiterate what I mentioned above: If you need to mutate an object in an array, just access it with a valid reference to it, or use -objectAtIndex. So long as you still have a valid claim on the object (a reference in this case, it's pointer didn't change because it was sent -retain) you can change it. Note the simple example below:
NSMutableString *str = [[NSMutableString alloc]initWithString:#"Hello"];
NSArray *arr = [[NSArray alloc]initWithObjects:str, nil];
NSLog(#"%#",arr);
[str appendString:#" Friend!"];
NSLog(#"%#",arr);
This prints:
2012-08-07 21:37:46.368 .MyApp[2325:303] (
Hello
)
2012-08-07 21:37:46.369 .MyApp[2325:303] (
"Hello Friend!"
)
Simple!
When i call the method:
- (void)removeObjectFromMediaAtIndex:(NSUInteger)idx;
which is one of the default methods in a file created as a core data object, i'm getting an error of unrecognized selector sent to instance. Anybody know why this might be happening?
Ensure that your NSManagedObject sublcass instance was created using an NSManagedObjectContext and not directly. Instead of leveraging #synthesize for properties, NSManagedObject sublcasses leverage the #dynamic keyword which indicates the accessors will be created at runtime - in this case, by the NSManagedObjectContext. They will not be there if you create the object instance using something like alloc]init];
It is a notorious Core Data bug. It is almost 2-year old but sadly it is still there. See this post: Exception thrown in NSOrderedSet generated accessors.
It sounds like you may have altered your data model without altering the classes, or vice-versa. Or perhaps one of your team members did (my team quickly learned about this danger). Another possibility is that the reference you are using is not actually the class you think it is. Sometimes if you overrelease an object, another object will occupy the previous memory space but it will not be the correct class.
However, this doesn't look like a default method. The default methods I am used to seeing are add object, remove object, change to a new NSSet, and one more that I can't quite remember off the top of my head. However, if you got the CoreData object to use an NSArray instead it would make sense.
In my iphone app i am programmatically creating the labels ,,i am creating array of labels
like UILabel *lblVersionName[20]; i need to copy the contents of the label into some string so i need to define property like
#property(nonatomic,retain)UILabel *lblVersionName[20];
but its giving error that "property can not have array of function type lblVersionName[20]"
cant we have property for array of labels(lblVersionName[20])
please somebody do help me, thanx in advance
Instead of C array just use NSArray or NSMutableArray
From the documentation:
Supported Types
You can declare a property for any Objective-C class, Core Foundation data type, or “plain old data” (POD) type
So you're trying to add a property for an unsupported type.
Like Terente wrote, you should use NSArray or NSMutableArray.
You might have a reason for why you need a c array, but that is only going to cause you a lot of trouble down the road. Don't fight the frameworks.
I'm working on iPhone and I'm using navigation.
I have list of data in RootViewController, and pass one data to detailViewController when a cell is clicked. Like this,
detailViewController.message = [tableData objectAtIndex:indexPath.row];
And I want to modify the content of 'message' in detailViewController. Is that possible?
I've tried that, but I get an error that it's immutable object. How can I do that? Somebody give me a hint. Thanks ;)
Added ------------------------------------------------
Ok. I'll specify the question.
in detailViewController, the message is decleared NSMutableDictionary* type.
and used like this.
NSMutableString *str = [m_message objectForKey:KEY_CONTENT];
[str appendFormat:#"appended!"];
And I've got this message.
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Attempt to mutate immutable object with appendFormat:'
Can't I just modify it's content like modifying data in c++ using pointer?
I think it would be best to use a delegate pattern for this. Create a DetailViewControllerDelegate protocol that informs its delegate of a changed message. Something along the lines of:
-(void)detailViewController:(DetailViewController *)controller didChangeMessage:(NSString *)message;
You could also directly manipulate the object by using a mutable one (NSMutableString, NSMutableArray etc.), but using a delegate improves reusability and decouples your classes.
EDIT:
The fact that your dictionary is mutable doesn't mean the object inside it are mutable as well. Your string str is probably immutable. Since NSMutableString is a subclass of NSString, the assignment will work though. You should make sure that you put a mutable string in the dictionary, or use the mutableCopy method of NSString to get a mutable copy of it.
It depends on what type of object you are passing. Immutable means that you cant alter the object. If you for exaple use NSArray, you have to switch to NSMutableArray instead. The same for string or dictionary.
Okay, i think i figured it out. The documentation for appendFormat says that appendFormat is for appending objects, just like when you use stringWithFormat.
The documentation states that:
The appended string is formed using
NSString's stringWithFormat: method
with the arguments listed.
You should use appendString to get the result you want.
I want to populate [MyClass class] from a JSON string.
I use json-framework to get the NSDictionary, and it's dead easy to instantiate and setValue: forKey:... on my data object.
But for more complex data objects with classes as members of MyClass,
ie:
MyOtherClass *classNoTwo
I tried with
Class test = object_getClass(myClass.classNoTwo);
id foo = [[test alloc] init];
But foo is nil/null. The only way I found to get around it is to in my init method of MyClass is to alloc memory for it, and later replace it.
I would also like to know how to get rid of the myClass.classNoTo reference, as I am not supposed to know all the properties in my general parser.
Please don't just tell me to read the documentation, because I've done that, and I can't figure it out.
Thanks in advance
Try calling class_getProperty() to access a property of a particular name and then property_getAttributes() on the property returned by the first function. This will return a string that encodes the property's attributes, including the type. The format of the string is explained in Property Type Strings in the documentation.
Finally, when you have derived the type of the property, use NSClassFromString() to instantiate an object.
Also see the docs for the two functions mentioned for more details.
I have written a very simple dependency injection container called Factory. I do not get your question entirely, but the problems we solve look similar. Take a look at my sources, they are very simple and should get you started. You might be interested especially in the ClassAnalyzer class. It’s just a hack, but you should be able to get what you want from there.