I'm trying to create a save & load module in my app. So the user can save some specific info and then load it at any point in time.
What I'm saving is an array of NSMutableStrings. I'm creating an iPad app so the saved info will be presented in a popover with a TableView.
So, here's the question. I would like to populate that tableView with my saved arrays, and for that I need to store my arrays somewhere. I'm new to objective-c and programming in general, and would like your advice on what's the best way of doing that.
Should I use a plist to store those arrays with Keys, so the keys will be the names that the user introduces when saving and also the name of the tableView cells? or maybe a simple NSMutableDictionary will do?
Please advise.
This answer might help you. Using Core Data might be overkill here, and saving to a plist is extremely easy. This is Benoît's answer from the linked question:
NSString *error;
NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES) objectAtIndex:0];
NSString *plistPath = [rootPath stringByAppendingPathComponent:#"yourFile.plist"];
NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:rootObj
format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];
if(plistData) {
[plistData writeToFile:plistPath atomically:YES];
}
else {
NSLog(#"Error : %#",error);
[error release];
}
where rootObj is the object you wish to serialize, in this case, your array/dictionary.
Also, if you are going to be read/writing to this data frequently during the course of your app, using a singleton which can make a huge difference performance-wise instead of constantly reading/writing from/to a file. You can load all of your data into the singleton on app-launch and save it upon applicationWillTerminate.
To answer your array/dictionary question, it depends on how you are obtaining your strings and how you want them to be ordered. Sorting an array is extremely easy, as you can see in this answer.
Sergey, based on your description, I would advise you look into using Core Data for data storage.
https://developer.apple.com/library/mac/#documentation/cocoa/conceptual/coredata/cdprogrammingguide.html
In addition to storing data, Apple has extended the use of Core Data in all sorts of neat ways, including the use of stored data to populate a UITableViewController through the use of NSFetchedResultsController
https://developer.apple.com/library/ios/#documentation/CoreData/Reference/NSFetchedResultsController_Class/Reference/Reference.html
That's it, give that a read and you should be well on your way.
Related
i need to store some objects from table.
It will be no more than 100 objects.
Is it good way to store it like array in NSUserDefaults? Or there is any better way?
Although you can store this is NSUserDefaults using [[NSUserDefaults standardUserDefaults] arrayForKey:#"key"]; you probably shouldn't. Defaults was designed to store VERY small ammounts of data, like a users preferences (thus the name). If you wish to store more data than this, then you may want to look into .plists, NSDocumentDirectory, Core-Data, or SQLite databases.
The better way would be to serialize it as a binary blob on disk using NSArrays writeToFile:atomically: or writeToURL:atomically:. NSUserDefaults aren't stored as binary and thus need extra parsing time upon loading, and extra time to write out to disk. NSUserDefaults is also not designed to hold large amounts of data but for a small set of settings data.
Store all custom data in NSDictionary or NSArray.
Now save dictionary or array with custom data in document directory follow this link
no Storing data on NSUserDefaults is not good, because it can cause a serious hack.
instead of it you can use AppDelegate to store data globally.
In my app I am working with the SimpleKML framework
https://github.com/mapbox/Simple-KML
I have some big files which takes about 5 seconds to process thought this library. I was thinking to cache the object in something like NSData.
I have read this tutorial from Apple:
https://developer.apple.com/library/mac/#documentation/cocoa/conceptual/Archiving/Articles/archives.html
But i dont really know of using nscoder is the best way to do this. Can someone point me in the right direction?
You want to use NSKeyedArchiver and NSKeyedUnarchiver.
If the object you're saving (and the objects it has as properties, and their properties, etc.) implement the NSCoding protocol then it's, as simple as
NSData *savedData = [NSKeyedArchiver archivedDataWithRootObject:someObject];
[savedData writeToFile:pathToSaveFile atomically:YES];
to archive the object into an NSData and then save it to disk, and then later
NSData *loadedData = [NSData dataWithContentsOfFile:pathToSaveFile];
SomeClass *foo = [NSKeyedUnarchiver loadedData]
to load the data and unarchive the object from the data.
If not, you'll need to override initWithCoder: and encodeWithCoder: for the objects in question to make them serialize properly.
My game comes with lots of .plist files containing many dictionaries, arrays, etc. They are about each party member's stats, info, etc.
A singleton is in charge of reading all those files and provide the necessary data for my game to run.
The game, at many points, will edit such values from the singleton, like a hero's level, stats, etc.
Eventually, the player will be given the option to "save" the game. My original idea was to basically tell the singleton to "overwrite" the .plist files within the project with the new edited data (the new data might have changes in stat entries etc, or even brand-new dictionaries representing new party members etc) and done.
But, I don't know how to do that, or even if it is possible.
I heard about NSUserDefaults, but I don't know if it suitable for what I am aiming, considering that the amount of dictionaries and arrays will be quite big, and that it is possible to keep adding up more dictionaries and arrays in the future. Imagine that the party can have as many members as you wish, for instance.
*Note: there are no multiple save files/profiles. When you press save, it saves, without asking anything else.
NSUserDefaults is not suitable for any substantial amount of data. Just write the plist to the documents directory, specify atomic:YES to insure the entire file is written.
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
If YES, the array (or dictionary) is written to an auxiliary file, and
then the auxiliary file is renamed to path. If NO, the array is
written directly to path. The YES option guarantees that path, if it
exists at all, won’t be corrupted even if the system should crash
during writing.
This method exists for both NSArray and NSDictionary,
Obtain the document directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:fileName];
BOOL status = [NSDictionary writeToFile:filePath atomically:YES];
NSDictionary could have ten NSArray depending on the top element of the plist.
Consider using CoreData.
NSUserDefaults is such an easy and convenient way to persist data on a device, and while it is encouraged as use for basic settings, I wonder, is there a practical limit to what you should use it for?
Suppose you have a large dictionary of many objects, 1000, and each of those objects is itself a dictionary with simple text strings as values. Overall, this big dictionary is probably not too large, since it only contains text, even if a fair amount of it.
Is it O.K. to use NSUserDefaults for something like this, your main data model?
Why not just store that as an NSDictionary in a file?
See this post for a nice way to save your file as a plist:
Save NSDictionary to plist
and getting it back is as easy as this:
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:fileName];
I want to save data locally but i do not know which method is better nsdictionary or plist?Can anyone tell which method is better and why?
Thanks in advance!
I think maybe what you meant to ask is which is better, plist or binary. If you save an NSDictionary to file using writeToFile: it will be stored as a plist. So in that sense there is zero difference between the two.
However, you also have the option of converting an NSDictionary instance into a serialized NSData representation, and then storing the serialized data as a binary file.
As for which is better and why, that depends upon what you want to do. The API for converting an NSDictionary to/from a plist file is more convenient to use than the API for serializing and reconstructing to/from NSData. However, storing an NSDictionary as a plist file only works if everything in the dictionary is a plist object (instances of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary) and if all of your keys are of type NSString. Otherwise your writeToFile: call will fail with frustratingly little information being provided about why.
So if your data structure meets the requirements for being stored as a plist and you cannot foresee it ever being changed such that it would no longer meet the requirements then you may find it more convenient storing it as a plist. Otherwise your only option is to do a binary serialization and storage using NSData. You may prefer this latter option if you want to have code that cannot be accidentally broken by someone sticking a non-plist-object in your data structure.