I have some trouble with compare two ALAssets object. I have two NSMutableArray: selectedImages and mutableAssets. I store there ALAssets object. But when i want to compare this assets it doesnt work for isEqual or containsObject method, only when i compare it by their url it works:
ALAsset *asset1 = [self.mutableAssets objectAtIndex:0];
ALAsset *asset2 = [self.selectedImages objectAtIndex:0];
NSLog(#"%#", asset1);
NSLog(#"%#", asset2);
if([self.selectedImages containsObject:[self.mutableAssets objectAtIndex:0]]) {
NSLog(#"the same1");
}
if([asset1 isEqual:asset2]) {
NSLog(#"the sames2");
}
if([asset1.defaultRepresentation.url isEqual:asset2.defaultRepresentation.url]) {
NSLog(#"the same3");
}
Gives only this line:
ALAsset - Type:Photo, URLs:assets-library://asset/asset.JPG?id=E8947286-22E2-42E4-A904-14D940A387B3&ext=JPG
ALAsset - Type:Photo, URLs:assets-library://asset/asset.JPG?id=E8947286-22E2-42E4-A904-14D940A387B3&ext=JPG
the same3
Why it happens?
seems like Assets don't implement isEqual:
I would not check the defaultRep's URL though... two different assets may have the same defaultRep in a way
I'd go with the ALAssetPropertyAssetURL for iOS 6+ or ALAssetPropertyURLs for ios4&5
--- you could wrap this in a category even!
#interface ALAsset (isEqual)
- (NSURL*)defaultURL;
#end
#implementation ALAsset (isEqual)
- (NSURL*)defaultURL {
if([[[UIDevice currentDevice] systemVersion] floatValue]>=6.0)
{
return [self valueForKey: ALAssetPropertyAssetURL];
}
else
{
return self.defaultRepresentation.url;
}
}
- (BOOL)isEqual:(id)obj {
if(![obj isKindOfClass:[ALAsset class]])
return NO;
NSURL *u1 = [self defaultURL];
NSURL *u2 = [obj defaultURL];
return ([u1 isEqual:u2]);
}
for iOS 4 and 5 and 6 and up
Background
containsObject: is determines whether anObject is present in the array by sending an isEqual: message to each of the array’s objects (and passing anObject as the parameter to each isEqual: message).
isEqual: is inspect whether two objects are the same. If two objects are equal, they must have the same hash value. hash means a table address in a hash table structure.
so, if not containsObject also not isEqual. Derive the results if you want to your ALAsset override isEqual.
NSURL, isEqual is two NSURLs are considered equal if and only if they return identical values for both baseURL and relativeString.
if([[[asset1 defaultRepresentation].url absoluteString] isEqualToString:[[asset2 defaultRepresentation].url absoluteString]])
{
}
else
{
}
Related
I'm stuck at following problem for quite some time now:
I've got two NSArrays, both containing NSManagedObject subclass-objects.
They're fed by different sources but the objects in them still have the same properties/values.
What I want to do now is check if array A contains objects from array B and vice versa.
Unfortunately NSArray's containsObject-method doesn't seem to work here.
I think it uses id-testing for the equality check on each object, doesn't it?
So, does anybody have a clue, what to try?
I even tried to encapsulate my objects in NSSets, using member: as my comparison-method but this didn't work out as well, especially because "you must not override" isEqual etc. for NSManagedObject subclasses.
Here's a code snippet:
//manufacturers is an array, parsed out of some xml here...
for(Manufacturer *manu in [fetchedResultsController fetchedObjects])
{
if(![manufacturers containsObject:manu])
{
NSLog(#"Deleting %#", manu.name);
[self.mContext deleteObject:manu];
}
}
for(Manufacturer *manu in manufacturers)
{
if(![[fetchedResultsController fetchedObjects] containsObject:manu])
{
NSLog(#"Adding %#", manu.name);
[newArray addObject:manu];
}
}
Thanks in advance for any hint ;)
I'm not sure if this works, but you could try to match the dictionaries you get with dictionaryWithValuesForKeys:.
Something like this:
NSArray *keysToCompare = [NSArray arrayWithObjects:#"FooAttribute", #"BarAttribute", nil];
// create an array with the dictionary representation of the managedObject
NSMutableArray *fetchedObjectsDictionaries = [NSMutableArray arrayWithCapacity:[[fetchedResultsController fetchedObjects] count]];
for (NSManagedObject *object in [fetchedResultsController fetchedObjects]) {
NSDictionary *dictionaryRepresentation = [object dictionaryWithValuesForKeys:keysToCompare];
[fetchedObjectsDictionaries addObject:dictionaryRepresentation];
}
// another array with dictionaries for managedObjects
NSMutableArray *manufacturersDictionaries = [NSMutableArray arrayWithCapacity:[manufacturers count]];
for (NSManagedObject *object in manufacturers) {
NSDictionary *dictionaryRepresentation = [object dictionaryWithValuesForKeys:keysToCompare];
[manufacturersDictionaries addObject:dictionaryRepresentation];
}
// compare those dictionaries
for (NSInteger i = 0; i < [fetchedObjectsDictionaries count]; i++) {
NSDictionary *dictionary = [fetchedObjectsDictionaries objectAtIndex:i];
if (![manufacturersDictionaries containsObject:dictionary]) {
// get the corresponding managedObject
NSManagedObject *object = [[fetchedResultsController fetchedObjects] objectAtIndex:i];
[newArray addObject:object];
}
}
if that won't work you can write your own isEqualToManufacturer: method and enumerate trough the arrays manually.
There would be 3 types of equality you can check for: same memory address, managed object id equality, and value equality. Your current code already checks to see if the objects share the same memory address and this is most likely not what you are interested in. This leaves two possible options. Using the managed object id equality method you can check if the manufacturers point to the same row in the database. Using the value equality you can check if two manufacturers are equal based on the shared values. Below is a way to check for NSManagedObjectID equality.
for(Manufacturer *manu in [fetchedResultsController fetchedObjects])
{
id databaseIDTest = ^(Manufacturer * checkManu, NSUInteger idx, BOOL *stop){
return [[checkManu objectID] isEqual:[manu objectID]];
};
if([manufacturers indexOfObjectPassingTest:databaseIDTest] == NSIndexNotFound)
{
NSLog(#"Deleting %#", manu.name);
[self.mContext deleteObject:manu];
}
}
for(Manufacturer *manu in manufacturers)
{
id databaseIDTest = ^(Manufacturer * checkManu, NSUInteger idx, BOOL *stop){
return [[checkManu objectID] isEqual:[manu objectID]];
};
NSArray * fetchedObjects = [fetchedResultsController fetchedObjects];
if([fetchedObjects indexOfObjectPassingTest:databaseIDTest] == NSIndexNotFound)
{
NSLog(#"Adding %#", manu.name);
[newArray addObject:manu];
}
}
You need to override -isEqual: since that's what -[NSArray containsObject:] calls into:
- (BOOL)isEqual:(id)other;
{
if (![other isKindOfClass:[Manufacturer class]]) {
return NO;
}
Manufacturer *otherManufacturer = other;
return ([self.name isEqual:otherManufacturer.name] &&
...
);
}
Checking for containment inside an NSSet is cheaper (and may make sense if you run into performance problems). It only works if you have a relatively decent -hash implementation, but it's easy to implement like this:
- (NSUInteger)hash;
{
return [self.name hash] + [self.foo hash] + ...;
}
Don't go trough too much trouble with the hash, just use 2 - 3 values that are most likely to uniquely identify the object.
I want to get the index of an object within the NSMutableArray of categories.
The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.
I have looked through the docs and can't find a simple way to go about this.
NSArray does not guarantee that you can only store one copy of a given object, so you have to make sure that you handle that yourself (or use NSOrderedSet).
That said, there are a couple approaches here. If your category objects implement isEqual: to match category_title, then you can just use -indexOfObject:.
If you can't do that (because the category objects use a different definition of equality), use -indexOfObjectPassingTest:. It takes a block in which you can do whatever test you want to define your "test" - in this case, testing category_title string equality.
Note that these are all declared for NSArray, so you won't see them if you are only looking at the NSMutableArray header/documentation.
EDIT: Code sample. This assumes objects of class CASCategory with an NSString property categoryTitle (I can't bring myself to put underscores in an ivar name :-):
CASCategory *cat1 = [[CASCategory alloc] init];
[cat1 setCategoryTitle:#"foo"];
CASCategory *cat2 = [[CASCategory alloc] init];
[cat2 setCategoryTitle:#"bar"];
CASCategory *cat3 = [[CASCategory alloc] init];
[cat3 setCategoryTitle:#"baz"];
NSMutableArray *array = [NSMutableArray arrayWithObjects:cat1, cat2, cat3, nil];
[cat1 release];
[cat2 release];
[cat3 release];
NSUInteger barIndex = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
if ([[(CASCategory *)obj categoryTitle] isEqualToString:#"bar"]) {
*stop = YES;
return YES;
}
return NO;
}];
if (barIndex != NSNotFound) {
NSLog(#"The title of category at index %lu is %#", barIndex, [[array objectAtIndex:barIndex] categoryTitle]);
}
else {
NSLog(#"Not found");
}
Not sure that I understand the question but something like this might work (assuming the Mutable Array contains objects of Class "Category"):
int indx;
bool chk;
for (Category *aCategory in theArray)
{
chk = ([[aCategory category_title] isEqualToString:#"valOfCategoryTitle"])
if ( chk )
indx = [theArray indexOfObject:aCategory];
}
Try this code much more simpler:-
int f = [yourArray indexOfObject:#"yourString"];
I'm trying to save all the variables in my class into NSUserDefaults using objc/runtime. And below is the code I'm using.
NSUInteger count;
Ivar *iVars = class_copyIvarList([self class], &count);
for (NSUInteger i=0; i<count; i++)
{
Ivar var = iVars[i];
NSString *varName = [NSString stringWithCString:ivar_getName(var) encoding:NSUTF8StringEncoding];
NSString *varType = [NSString stringWithCString:ivar_getTypeEncoding(var) encoding:NSUTF8StringEncoding];
if([varType hasPrefix:#"["])
{
NSLog(#"Array");
id var1 = [_manager valueForKey:varName];
NSLog(#"--- %#", var1);
NSData *data = [NSData dataWithBytes:&([_manager valueForKey:varName]) length:sizeof([_manager valueForKey:varName])]
[[NSUserDefaults standardUserDefaults] setObject:[_manager valueForKey:varName] forKey:varName];
}
else
{
NSLog(#"NonArray");
NSLog(#"--- %#", [_manager valueForKey:varName]);
[[NSUserDefaults standardUserDefaults] setObject:[_manager valueForKey:varName] forKey:varName];
}
}
free(iVars);
The problem is that, when there are only primitive datatypes, the above code works just fine. But, when I try to access a array variable like int[], or float[], it gets crashed with SIGABRT. it is not showing any other messages.
valueForKey doesn't return any values for C arrays.
If anybody know how to load values for C-arrays in runtime, please help.
Thanks in advance,
Suran
Unless you always provide a paired length method, your program will never know the length of the array returned. So... you will need to do some work someplace to accomplish this without a crash.
If I really wanted to do what you're doing, I would make the class itself create the array, providing NSData. If this is common, you may want to use a convention:
- (int*)pixelBuffer;
- (NSData *)pixelBufferForSerialization; // << returns a deep copy of
// self.pixelBuffer as an
// NSData instance.
So your above implementation would see that the property defines a scalar array, and then request NSData * data = obj.pixelBufferForSerialization; instead of trying to produce the data itself.
Update
It's best to let the class do it. Here's how to create NSData using such an array:
#interface DataManager : NSObject
{
#private
int* things;
size_t nThings;
}
- (int*)things;
- (NSData *)thingsAsNSData;
#end
#implementation DataManager
- (int*)things
{
return things;
}
- (NSData *)thingsAsNSData
{
// note: you may need to choose an endianness for serialization
if (0 == nThings) return [NSData data];w
return [NSData dataWithBytes:things length:nThings * sizeof(things[0])];
}
#end
Again - you want the class to create the data because it knows its own structure best.
Hi I am woundering if you can check to see if a NSString equals a specific value say for instance a name of a person?
I am thinking along the lines of
if (mystring == #"Johns"){
//do some stuff in here
}
if ([mystring isEqualToString:#"Johns"]){
//do some stuff in here
}
Here is another method you might want to use in some circumstances:
NSArray * validNames = #[ #"foo" , #"bar" , #"bob" ];
if ([validNames indexOfObject:myString].location != NSNotFound)
{
// The myString is one of the names in the valid names array
}
Or if you have a large amount of names in the array you could use a NSSet, since finding an object is faster than in an array ((O(Log N) vs O(N))
NSSet * validNamesSet = [NSSet setWithArray:validNames];
if ([validNamesSet containsObject:myString])
{
// This is faster than indexOfObject for large sets
}
These methods work because NSSet and NSArray use isEqual: which will call isEqualToString: for NSString instances.
I have a NSMutableArray which contains a few NSString objects. How can I test if the array contains a particular string literal?
I tried [array containsObject:#"teststring"] but that doesn't work.
What you're doing should work fine. For example
NSArray *a = [NSArray arrayWithObjects:#"Foo", #"Bar", #"Baz", nil];
NSLog(#"At index %i", [a indexOfObject:#"Bar"]);
Correctly logs "At index 1" for me. Two possible foibles:
indexOfObject sends isEqual messages to do the comparison - you've not replaced this method in a category?
Make sure you're testing against NSNotFound for failure to locate, and not (say) 0.
[array indexOfObject:object] != NSNotFound
Comparing against string literals only works in code examples. In the real world you often need to compare against NSString* instances in e.g. an array, in which case containsObject fails because it compares against the object, not the value.
You could add a category to your implementation which extends NS(Mutable)Array with a method to check wether it contains the string (or whatever other type you need to compare against);
#implementation NSMutableArray (ContainsString)
-(BOOL) containsString:(NSString*)string
{
for (NSString* str in self) {
if ([str isEqualToString:string])
return YES;
}
return NO;
}
#end
You may also use a predicate:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"SELF IN %#", theArray];
BOOL result = [predicate evaluateWithObject:theString];
for every object
[(NSString *) [array objectAtIndex:i] isEqualToString:#"teststring"];