I'm currently looking for the best way to save data in my iPhone application; data that will persist between opening and closing of the application. I've looked into archiving using a NSKeyedArchiver and I have been successful in making it work. However, I've noticed that if I try to save multiple objects, they keep getting overwritten every time I save. (Essentially, the user will be able to create a list of things he/she wants, save the list, create a few more lists, save them all, then be able to go back and select any of those lists to load at a future date.)
I've heard about SQLite, Core Data, or using .plists to store multiple arrays of data that will persist over time. Could someone point me in the best direction to save my data? Thanks!
Core Data is very powerful and easy to use once you get over the initial learning curve. here's a good tutorial to get you started - clicky
As an easy and powerful alternative to CoreData, look into ActiveRecord for Objective-C. https://github.com/aptiva/activerecord
I'd go with NSKeyedArchiver. Sounds like the problem is you're not organizing your graph properly.
You technically have a list of lists, but you're only saving the inner-nested list.
You should be added the list to a "super" list, and then archiving the super-list.
CoreData / SQL seems a bit much from what you described.
Also you can try this framework. It's very simple and easy to use.
It's based on ActiveRecord pattern and allow to use migrations, relationships, validations, and more.
It use sqlite3 only, without CoreData, but you don't need to use raw sql or create tables manually.
Just describe your iActiveRecord and enjoy.
You want to check out this tutorial by Ray Wenderlich on Getting started with CoreData. Its short and goes over the basics of CoreData.
Essentially you only want to look at plists if you have a small amount of data to store. A simple list of settings or preferences. Anything larger than that and it breaks down specifically around performance. There is a great video on iTunesU where the developers at LinkedIn describe their performance metrics between plists and CoreData.
Archiving works, but is going to be a lot of work to store and retrieve your data, as well as put the performance challenge on your back. So I wouldn't go there. I would use CoreData. Its extremely simple to get started with and if you understand the objects in this stack overflow question then you know everything you need to get going.
Related
So i'm following the ios tutorial here
http://developer.apple.com/library/ios/documentation/iPhone/Conceptual/SecondiOSAppTutorial/Introduction/Introduction.html#//apple_ref/doc/uid/TP40011318-CH1-SW1
The data for the tableview is a custom class containing just strings and dates.
Here is what it looks like
http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/SecondiOSAppTutorial/DesigningDataModel/DesigningDataModel.html
Can anyone suggest how to save this to data between launches of the app?
What about making the app Document based .. i.e. using UIDocument?
You could use NSCoding to store such simple data. You could probably even use NSUserDefaults but I wouldn't recommend it. Core Data is really the way to go unless you know you'll never need anything slightly more complex.
Check out this guide on how to persist simple data using NSCoding from www.raywenderlich.com - a really good tutorial site for people beginning iOS development.
You could use NSCoding or NSUserDefaults.
But for any real application that has a lot more than sample data you'll be looking at something like Core Data eventually.
From your comments I see that you think it's overkill for just a couple of fields. However, this is an ideal time to learn about and practice setting up a Core Data model and connecting it to a table view with a Fetched results controller.
I'm writing an iOS applications that saves Music albums(just an exercise I'm doing for the fun of it) .
For every Album there's a singer, song names, time, and a picture
The final result will be a lot of objects with a lot of details including a picture attached to every object. Should I even consider doing something like that with plist? (can pictures be stored in a plist?)
What's the best way to save and access that data?
I'm new to iOS and from the training videos I've seen Core Data is not recommend for the beginner user. Is that really the case?
If I'm going with plist, should I create one plist for every genre for example rap.plist , rock.plist etc' or just a big data.plist?
Thanks
I would go for core data. If you choose the right template when you create your new project in xcode then reduce the once-off overhead work significantly.
With that simple structure I would say that the templates provides nearly everything you need. Just define your model and layout and off you go.
There is just the images where I would spend a bit more time in thinking it over. I personally never put the image data into core data itself. I rather stored them as file and within my core data model I just stored the path and filename to access it. As file name I simply used a timestamp. You could use some auto-increment or other unique id technique but a time stamp would do as well. It will not be visible to the user anyway.
I think the best way you can do this, since you are new to IOS is by using sqlite. Save all the information you want in your local database and display it on the screen.
You can use plist if you have data structure that is small.
Note that property lists should be used for data that consists primarily
of strings and numbers. They are very inefficient when used with large blocks
of binary data. A property list is probably the easiest to maintain, but it will be loaded into memory all at once. This could eat up a lot of the device's memory.
With Sqlite you will easily be able delete , edit, insert your data into the database.
Core data also uses sqlite for data storage only it helps you to manage your data objects, their relationships and dependencies with minimal code.
And since your are new getting started with core data would not be such a good idea i think.. so i would suggest start off with normal sqlite. Save the data in one of your folders of your app and store their path in the database.
You dont have to write different plists.. You can use the same one if you are using.
EDIT : here is a link that will help you with learning sqlite
http://www.iosdevelopment.be/sqlite-tutorial/
you need some more code to set up the core data stack (the store coordinator, the store, the object model, and a context)
it is a tad more complicated but that shouldnt scare you off.
Reading a plist is indeed dead easy but while good for smaller data (like the info.plist) it doesnt scale and soon you need a fullblown DB
As you edited your original question an decided to go with plist now.
In that case I would go for one plist per ablum and one overall plist for the list of albums.
You could, of course, use more plists for categories etc.
However, if you are thinking of data structures like categories you are far better off with core data. Especially when it comes to searching.
No one seems to be mentioning SQLLite, I would go that way and for reasons that I explain here ( https://stackoverflow.com/a/12619813/1104563 ). Hope this helps!
coredata is a apple provided persistant tool, while plist is XML file. The reason why core data is not recommended for beginner, I think, is core data is more difficult than plist from programming perspective. For your application, obviously core data is more suitable. But alternatively, you may also use archive file, that's between core data and plist.
I need your advise on this, I'm currently developing a kinda family application.(Everything relates to the family)
I would like to add something similar to a family tree or the family members. (Using Table view) and each member/element on the list will have its own "view" containing a 50 words biography about him and his photo.
Since, I'm still new to iOS development and I still haven't worked with SQLite yet. Do you guys think SQLite is the best for this job? How about the photos. Is there a way to put a thumbnail photo for each member?
SQLite does this well, though Core Data is generally considered the preferred iOS technology. There are a few situations where I might advise using SQLite over Core Data, but you haven't outlined any app requirements that would make me lean that direction.
If you do your own SQLite, though, I'd suggest you use something like FMDB, so you spare yourself the hassles of writing SQLite code.
And, as I mentioned in the comment of another answer to this question, regarding images in Core Data or SQLite, you face a significant performance hit for that. If you're dealing with small images (e.g. thumbnails), it's fine, but if you're dealing with a lot of large images, you really might want to consider storing them in some directory structure under the Documents folder (and then store relative path names in your database). It not architecturally elegant to take the images out of the database and use the Documents folder, but for performance reasons you might want to do precisely that.
No. I would use CoreData for this. CoreData gives you the graphical modelling tools to build an object model and handles all the tedious housekeeping required to persist your object graph to disk.
The photos you would store as conventional files on disk and be modelled by a CoreData object that maintains a reference (URI or file path) to the photo.
I would use CoreData for this, it boils down to an SQLite database, but Apple have added their own wrapper round the SQLite database, making it really simple to use.
There are a number sample apps on the Developer Site as well as numerous Tuts available just by searching the phrase "CoreData example" in google, the link here is ro Raywenderlich which is a good place to start. I think once you go through this blog you'll be using CoreData more and more when you need to store things like this.
With regards to the thumbnail storage I would store those on the device and save the path to the file in the Database.
Yes you can use SQLite for this; in fact it's ideal for holding a family tree given its relational nature.
The photo data can be serialised into a byte stream (NSData *) and stored in a column as a blob.
A database has the huge pro, that you can keep everything stored at one place.
You could (not that I recommend) also use a folder-structure to specify the data like /images/, /words/, /people/ and use the same name for everyone throughout the folders (tim.jpg, tim.txt, tim.dat )
Or use a small database to store everything in different tables all with relation to your "family(_members)" table.
You can also store images in a database, mostly as a blob (or base64 encoded or or or... yuck)
I don't know how well iOS stuff handles those database types of SQLite but you should be better of using a database for that.
You have a number of options here.
If you are storing all of the info within the application itself (ie. the details aren't being fetched from the web somewhere), SQLite (as a CoreData backend) would probably be a good idea. Read up on using CoreData so that you don't end up reinventing the wheel, and so that your implementation provides a smooth scrolling experience that iPhone users expect.
The photos, however, need a different means of storage/retrieval.
A common technique is to implement a 2-level cache system. What this would entail is storing the pictures in individual files, but keeping some of them in-memory after they are retrieved for speed. You could then have a class that looks something like the following:
#interface ThumbnailManager : NSObject
{
id<ImageCache> _imageCache; // You make this.
}
- (UIImage *)imageForFamilyMemberWithName:(NSString *)name;
#end
That's similar to something I would do in your position.
Good luck!
I am pulling data from an API and then building out my data objects with it. I want to cache this data for the future. I have been storing the string from the api in NSUserDefaults and then re-parsing it each time the app loads. This works, but it really seems like the wrong way to go about it.
How can I do this?
Have you noticed the NSCache?
An NSCache object is a mutable collection that stores key-value pairs, similar to an NSDictionary object. The NSCache class provides a programmatic interface to adding and removing objects and setting eviction policies based on the total cost and number of objects in the cache...
Personally I'm quite fond of the EGOCache classes, I use them quite a lot in my projects:
https://github.com/enormego/EGOCache
The classes are easy to use, I used to have my own classes with a similar design, but these are just more well-rounded, so I decided to stick with them (don't wanna reinvent the wheel).
There are many different solutions to this problem and there is no "right" way to do it. A few popular options are:
Core Data - Apple's framework for persistence. Very performant, but more difficult.
SQLite - Fast and flexible, but bare bones.
Plists - Basically writing a file to disk, you have to read and write manually.
NSUserDefaults - The lightest weight "key-value" option.
I would encourage you to read up on all four and see which one works best for you.
I vote Core Data
What type of data? If its text/string bases SQLLite would probably be the best.
I'd store the computed/parsed data in either a Core Data store, or in NSData flat files in your application's Documents directory. You're correct that storing that in NSUserDefaults and then re parsing feels a little overkill.
What am I trying to do?
A UI process that reads data from a Core Data store on disk. It wouldn't need to edit the data, just read and display the data.
A command line process that writes to the same data store as accessed by the UI.
Why?
So that the command line process can be running all the time but the user can quit the UI process and forget about the app until they need to look at the data it's captured.
What would be the simplest and most reliable way of achieving this?
What Have I Tried?
I've read up on sharing a data store between threads and implemented this once before, but I can't find anything in the docs or on the web indicating how to share a store between processes.
Is it as simple as pointing both processes at the same data store file? I've experimented with this briefly. It appeared to work OK, but I'm worried I might run into problems with locking etc when it's really put under stress.
Finally
I'd really appreciate someone giving me pointers on what direction to go with this. Thanks.
This might be one of those situations in which you'll simply have to Try It And See™.
Insofar as I can remember, SQLite (which is the data store you'll most likely want to be using) has built in mechanisms for file locking and so on; so the integrity of the file is likely to be assured. If, on the other hand, you use the CoreData/XML approach, you might run into problems.
In other words; use the SQLite backing for your file, and you should likely be fine.
You can do exactly what you want, you probably want to use the SQLite store otherwise saving and committing every time you want to synch out data will be horrifically slow. You just need to use some sort of IPC doorbell between the apps so that you can inform one app it needs to recheck the persistent store on disk and merge in its data.
Apple documents using multiple persistent store corindators as a valid option in Multi-Threading with Core Data (in "General Guidelines", open 2). That happens to be discussing completely parallel CD stacks in the same process, but it is valid if they are in completely separate address spaces as well.
Nearly two years on, and I've just found a much better way of doing this.
The answer seems to lie with Sync Services. I didn't even realise it existed! There's an excellent post about this at:
http://www.timisted.net/blog/archive/core-data-and-sync-services/
I've not tried this with my app yet, but it seems like an excellent way of sharing a core data store between two processes or applications.
If I experience any performance issues, I'll update this answer accordingly, but this seems like the Apple recommended way of doing it.
You need to re-think your architecture. If you want a daemon to own the data store, then have your GUI app connect to the daemon. Trying to share the data store is a can of worms you don't want to open.