Currently I'm saving bookmarks in NSMutableIndexSet
- (BOOL)saveBookmark
{
if (!bookmarkIndex) {
bookmarkIndex = [NSMutableIndexSet indexSet];
}
if (currentIndex) {
[bookmarkIndex addIndex:currentIndex];
return [bookmarkIndex containsIndex:currentIndex];
}
return NO;
}
But when I exit the app and come back to check on bookmarks, the bookmarks are not showing then.
So thinking of storing bookmarks in NSUserDefaults.
Is it possible to store NSMutableIndexSet in NSUserDefaults or only NSMutableArray can be saved in NSUserDefaults.
Is there is any example of storing NSMutableIndexSet in NSUserDefaults?
Appreciate help.
Thanks
In NSUserDefaults all you can store are property lists. Read more about them here:
https://developer.apple.com/Library/ios/documentation/Cocoa/Conceptual/PropertyLists/AboutPropertyLists/AboutPropertyLists.html#//apple_ref/doc/uid/10000048i-CH3-54303
As you can see, you cannot store a NSIndexSet in a property list, so you will need to use either a NSArray or a NSDictionary. I do not see any reason why cannot you store an array.
See the answer below on how to get indexes into an array:
How to get indexes from NSIndexset into an NSArray in cocoa?
Related
I'm stuck at json object parsing really tried hard. The problem is how to parse the json object. Here's what i get the response in the log.
{"0":{"**title**":"Test Event","url_title":"test_event1","status":"open","entry_date":"Sep 10, 2012,
05:20:38AM","entry_id":"26","site_id":"1","channel_id":"3","field_dt_40":null,"field_dt_58":null,"channel_title":"News &
Events","channel_name":"news_events","start_date":"1348120800","end_date":"1348120800","start_time": "43200","end_time":"46800","where":"FCF","news_event_description":"<p>\n\tLunch with group.<\/p>\n"},
"1":{"**title**":"Test Event 2","url_title":"test_event_2","status":"open","entry_date":"Sep 10, 2012, 05:20:08AM","entry_id":"28","site_id":"1","channel_id":"3","field_dt_40":null,"field_dt_58":null,"channel_title":"News & Events","channel_name":"news_events","start_date":"1348207200","end_date":"1348207200","start_time":"43200","end_time":"46800","where":"FCF - Lunch","news_event_description":"<p>\n\tThis was a great event.<\/p>\n"},
"2":{"**title**":"Test Event 3","url_title":"test_event_3","status":"open","entry_date":"Sep 10, 2012, 05:20:54AM","entry_id":"29","site_id":"1","channel_id":"3","field_dt_40":null,"field_dt_58":null,"channel_title":"News & Events","channel_name":"news_events","start_date":"1346738400","end_date":"1346738400","start_time":"7200","end_time":"11700","where":"FCF - Lunch","news_event_description":"<p>\n\tFall planning season.<\/p>\n"}}
The problem is i want to show all the titles in the tableview. I can get the single Title by using key 0,1,2. But i want all the titles to be shown at once i parse
Please help me out guys, Thanks in advance.
Suppose jsonDict is your json dictionary.... Try this
NSArray * keys=[[NSArray alloc]init];
keys=[jsonDict allKeys];
NSMutableArray *titles=[[NSMutableArray alloc]init];
for(int i=0;i<[keys count];i++){
[titles addObject:[[jsonDict valueForKey:[keys objectAtIndex:i]]valueForKey:#"title"]];
}
NSLog(#"your array of titles : %#",titles); //use this array to fill your cell
Are you trying to parse the JSON yourself? You might find it easier to use something that's already well tested, such as TouchJSON or Apple's own NSJSONSerilization. The result should be a graph of Objective-C objects that you can use however you like.
In any case, what you've got there is the equivalent of a dictionary of dictionaries. If you have that as a NSDictionary called myJSONDictionary, you can say:
NSArray *theObjects = [myJSONDictionary allValues]; // gets all the objects
NSArray *theTitles = [theObjects valueForKey:#"**title**"]; // gets all the titles
You can also iterate through a dictionary using fast enumeration:
NSMutableArray *theTitles = [NSMutableArray array];
for (NSString *key in myJSONDictionary) {
NSDictionary *object = [myJSONDictionary objectForKey:key];
NSString *title = [object objectForKey:#"**title**"];
[theTitles addObject:title]
}
There's no real advantage to doing that instead of using KVC as in the first example if you just need the titles, but it could be the right choice if you have more complex work to do for each object.
I may be phrasing the question incorrectly based on my situation - sorry if that's the case.
Here's the issue: In a previous version of my app, I'm saving an NSMutableArray to a plist using NSCoding.
In a new version, I've added settings data, so I now put the previous array and the new data in an NSDictionary then use NSCoding. Works fine.
However, for this release, I'll have to determine if an existing plist is the old version (NSMutableArray) or the new one (NSDictionary).
The basic code is this:
NSData *codedData=[[NSData alloc] initWithContentsOfFile:plistPath];
//EITHER this (array): allMsgs=[NSKeyedUnarchiver unarchiveObjectWithData:codedData];
//OR this (nsdict): tmpdict=(NSDictionary *)[NSKeyedUnarchiver unarchiveObjectWithData:codedData];
How can I read the plist and determine if it's an NSDictionary or NSMutableArray without throwing errors?
Just store the unarchived object as an id, then use isKindOfClass: to check its class:
id unarchivedObject = [NSKeyedUnarchiver unarchiveObjectWithData:codedData];
if ([unarchivedObject isKindOfClass:[NSArray class]]) {
// do something
} else if ([unarchivedObject isKindOfClass:[NSDictionary class]]) {
// do something else
}
I create a custom object that has some properties like ID and Title,description etc...
And I add it to an array. (That array may contains more than 500 values).
And I use the following code to retrieve custom objects,
-(CustomObjects *)getObjectWithId:(int)id {
CustomObjects *objCustomObjects = nil;
for (CustomObjects *customObjects in arrayCustomObjects) {
if (customObjects.id == id) {
objCustomObjects = customObjects;
break;
}
}
return objCustomObjects;
}
But It has some performance problem, because I use the function to call on UIScrollview pinch.
How can I improve performance in fetching the objects?
thanks in advance,
A dictionary is better for this. The only catch is that you can’t have a NSDictionary with primitive int keys, so that you have to wrap the id in an NSNumber.
- (void) addCustomObject: (CustomObject*) obj {
NSNumber *wrappedID = [NSNumber numberWithInt:[obj idNumber]];
[dictionary setObject:obj forKey:wrappedID];
}
- (CustomObject*) findObjectByID: (int) idNumber {
NSNumber *wrappedID = [NSNumber numberWithInt:[obj idNumber]];
return [dictionary objectForKey:wrappedID];
}
A dictionary (also called hash table) does not have to go through all the values to find the right one, it has all the values arranged cleverly according to the keys so that it can jump to the right one or close to it. What you are doing with the array is called linear search and it’s not very efficient.
Better you can use NSDictionary with id as the key. You can easily fetch the object from the dictionary.
Is it Ok for your requirement?
You could use an NSPredicate that checks whether id equals the one you're looking for, and simply filter the custom objects using this predicate by calling filteredArrayUsingPredicate:.
To improve performance, I would try to postpone whatever you're trying to calculate by not directly calling the function that does the heavy work in your scroll view, but rather call [self performSelector:... withObject:nil afterDelay:0]; which postpones the calculation to the next runloop cycle. If you check if there's already a calculation scheduled before you call performSelector you should actually be able to reduce the frequency of the calculation while maintaining a crisp interface.
You must ditch the array in favor for a dictionary if you want to have fast lookups.
If you want to access objects both by key and index then you need to the objects around in two collections, and make sure they are in sync.
I have already done a helper class for this named CWOrderedDictionary. It's a subclass of NSMutableDictionary that allows for access to objects by both keys (as any dictionary do), and by index using methods identical to NSMutableArray.
My class is available to use for inspiration or as is from here: https://github.com/jayway/CWFoundation/
Use NSPredicate:-
You will receive the filtered array with the object that has the id you passed;
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"id == %#", id];
NSArray *filtered = [arrayCustomObjects filteredArrayUsingPredicate:predicate];
Instead of intjust use [NSNumber numberWithInt:] , i did some changes in your given code.
-(CustomObjects *)getObjectWithId:(NSNumber* )id {//changed int to NSNumber
CustomObjects *objCustomObjects = nil;
NSPredicate *bPredicate = [NSPredicate predicateWithFormat:#"SELF.id==%#",id];
NSArray *result = [array filteredArrayUsingPredicate:bPredicate];
//return filtered array contains the object of your given value
if([result count]>0)
objCustomObjects = [result objectAtIndex:0];
}
return objCustomObjects;
}
i am wondering how its possible to add an index for a tableview to an array. i am trying to save this index to the array in order to be able to view it later. i just am interested in knowing how to save the index to the array. thanks
Use a NSMutableArray and send it an addObject: message with the NSIndexPath as an argument.
Same way you save anything to an array:
NSMutableArray *myArray = [NSMutableArray array];
[myArray addObject:myIndexPath];
I have the Array defined below.
NSMutableArray *tempMPArray = [NSMutableArray arrayWithCapacity:16];
for (int i=0; i < chapters; i++)
{
[tempMPArray addObject:[NSNull null]];
}
Every time I use it as a one of the objects of a dictionary below to register default values it crashes with EXC_BAD_ACCESS.
[[NSUserDefaults standardUserDefaults] registerDefaults:myDict];
If I replace the objects in the array with any other object NSNumber etc it works fine. What am I doing wrong with my array that NSUserDefaults rejects it ? The stack trace or NSZombie does not give any additional info.
While the solution may be a "work-around" I don't think it answers the underlying question. By providing a dictionary with [NSNull null] values he is providing NSUserDefaults with a valid dictionary. Why is it crashing? Is it something he is doing "wrong" or is it a bug in registerDefaults?
There may be circumstances where it is important to know whether say a user has entered a value (ie there is a valid string) or not entered a value (null) and the method of creating a "valid but empty string" can't determine if the empty string was because the user created a string with no characters or if he had never created a string at all. You may want different logic in these two cases.
I'm in the same boat, I have an NSUserDefault value I want to be [NSNull null] and everything I've read suggests the "right" way to put a null value in a dictionary is with [NSNull null] and my dictionary creates fine. But registerDefaults with this valid dictionary causes a crash. That suggests a bug in the implementation of registerDefaults doesn't it? What is wrong with the following and why does it crash?
NSArray *defaultValues = [NSArray arrayWithObjects:[NSNull null], nil];
NSArray *CurrentKeys = [NSArray arrayWithObjects: #"NullKey", nil];
NSDictionary *resourceDict = [NSDictionary dictionaryWithObjects:defaultValues forKeys:CurrentKeys];
[[NSUserDefaults standardUserDefaults] registerDefaults:resourceDict];
Ultimately, i think the answer is that the userDefaults get written out as a plist and plists don't support NSNull. if that's the case, the documentation for registerDefaults should say that only plist object types are allowed in the dictionary
Here's a better solution!
Define a static after #implementation
NSString *const Null = #"";
Then
NSMutableArray *tempDSArray = [NSMutableArray arrayWithCapacity:16];
for (i=0; i < chapters; i++)
{
[tempDSArray addObject:Null];
}
Everything else should work fine!