I am new to iPhone app development and have a question about storing data. I've spent quite sometime learning about core data but still confused about the concept of persistence store.
What I understand is that core data is just a way of managing the data you downloaded from an external database. But given that core data is backed by SQLite, does that mean there exists a SQLite db in-memory while running? If so, does that mean when I use core data it will be more effective if I download a huge data set at start? But what about apps such as twitter or Facebook that require constant update of data, is a straight $NSURLConnection$ sufficient in these cases? If core data is used, will the extra overheads (i.e. data objects) be of any burden for such frequent request of update?
I would also like to find out some common ways of setting up an online database for iPhone app? Is it usually MySQL servers with a homemade Python wrapper that translates the data into JSON? Any standard server provider would provide the whole package? Or open source code?
Many many thanks!
I'm going to go through and try to address each of your questions, let me know if I missed one!
Firstly, Core Data can be used to store information generated in your app as well, there is nothing keeping you from using it in one way or another.
The way I understand it working is that the file, or other storage mechanism Core Data uses, exists regardless of whether or not your app is running. For a user to have to wait for a large database to be downloaded and loaded into a local database without being able to interact with your application is not the best way to do it in my opinion, people react negatively unresponsive UI. When a user may run your app for the first time, its possible you may need to get a larger set of data, but if any of it is generic and can be preloaded that is ideal, the rest should be downloaded as the user attempts to access it.
Facebook and Twitter applications work just as you understand in that a connection is established and the information is pulled from the appropriate site, the only thing they store is profile information, as far as I know. I would hesitate to use Core Data to store peoples information as eventually yes, there would be a significant amount of overhead caused by having to store peoples news feed or messages going back months on end.
As for setting up on online database that is something I'm unfamiliar with, so hopefully someone else can provide some insight on that, or if I find something I think may be of use, I will post back here for you. This part may actually merit its own separate question.
Let me know if you need to me elaborate on anything!
Related
I have a rather simple idea for an iPhone app. What I need to accomplish:
Allow login of users (which means I'll have to store usernames, passwords, and other account info).
Allow users to submit strings that other users can view.
Attributes attached to each string that must be tracked (i.e. "votes, views, comments, etc.).
As such, I assume I'll need to start learning about databases and working between a server and client. I've gotten my feet wet in OSX/iOS programming (specifically Objective-C) before. I want to learn how one can accomplish a data-based application and the needs I listed above.
I've done some light research and discovered something called SQLite (free and open-source is always good). Is this the right path to achieve what I want to do? I'm a total "noob" when it comes to this field of server/client/data "stuff".
Your help is greatly appreciated.
SQLLite is more like a local database. Really, the database that you will use is unimportant. It sounds like a project with webservices. Inside your webservices, you might connect to a Microsoft SQL Server or anything you want.
I think you should study how to setup a webservice that can be accessed in your code. Webservices is not an Objective-C topic, it applies to any platform. Your project is more like a web development project.
You can save user's credentials in keychain.
#Kinderchocolate is right about introducing database into your project.
It hears about a app which need transmitting data among clients.It means your need server database and local database.
For server database,I recommend you to use Parse.Parse is a platform which provide a convenient way to use their server database with Objective-c in your app.This tool will save many times and energy(it's not necessary to learn PHP,Apache,Mysql).Parse is not free of course,but it has a free period and enough for you to examine your idea.
Here's Parse!.
For local database,I recommend you to use Core Data,Which is provided by XCode.Core data is so strong to meet your need.You can find a way to use Core Data in many books.
Go try Firebase for database in the cloud. (On the server). In Swift 4 there is complete support for Firebase and SQLite
I have started development of an app which is data reliant. It has a lot of information (using probably only 2 tables) so I am thinking core data is the way to go. However, I hate apps that only work when the user has an internet connection.
So what I would like to do is have saved core data on the device, and only download updates either periodically, on users' request or give them the option to update data when the app has loaded.
Is this the best solution and could someone please point me in the direction of a good blog or tutorial for this.
Many Thanks
The topics you ask about are really unrelated.
To implement your apps data model, Core Data is a fine solution. The iOS docs and sample code are good. if you need more I'm sure there are various blog posts but I don't have a recommendation. If you run into specific problems/issues there is tons of stuff on SO as well.
If you don't want to require a connection that's fine. This has nothing do with core data. It does have to do with apps functional requirements. At a minimum, store the apps current state in the data model and update at whatever interval you like, checking for a connection if that's required. Basically, whatever your app does, if a function requires a connection reflect that in the UI. Everything else should work fine without a connection.
I am creating a Questions and answers app for iphone which allows user to answer the questions displayed.
Currently I am invoking a web service to store the users answers. But I am slightly worried what if the web service goes down. I need to store the users answers locally and then invoke the web service when it is up and running.
How can I store the users answers when the web service is down. Is Sqllite a good option for this?
Please suggest.
Thanks,
Is Sqllite a good option for this?
Yes, SQLite is decidedly a good option. The other choice would be Core Data.
Use CoreData or SQLite on iPhone?
It depends on the complexity of your data model. I've looked into something like this recently and here is what I learnt. The most popular data storage methods in the iPhone are:
plist
Good for small quantities (hundreds of Ks) of hierarchical data.
Bad if relationships or queries are complex (since you have to write the code).
Very easy to learn.
Supports array, dict, string, data, date, integer, real, boolean elements.
You can store it as XML, which is editable and portable, or as binary files, which is faster.
Core Data
It's a object graph manager with searching and persistent functionality.
You need a good few hours of learning.
Easy to use once you set it up.
Better than a plist because it lets you manage object graphs, grow your object model, write queries, undo/redo, migrations to modified data models, memory management, and handle concurrent access.
Better than SQLite because:
The performance is similar and the speed of development is faster.
Creating objects is faster.
When the objects are in memory, executing queries doesn't require a search in the backend (which usually is either memory or SQLite).
SQLite
A database.
Better than Core Data when the operation doesn't require you to bring objects to memory. Example: update, delete, and select 1 (see if something exists).
It has full text search if you compile the extension.
Hardest to learn. Easier if you use a wrapper: FMDB, egodatabase.
If you can get away with a plist do that. If you see the amount of code you will have to write is too much work, then switch to Core Data. Only if you are an expert and absolutely need the performance use SQLite (unless, of course, you already know SQLite and not Core Data).
It should be, yes. I'd set up a Core Data based app with entities for Questions and Answers and set up relationships between them. Then just use NSFetchedResultsController or whatever you would like to gather and display the data
You have several options:
Sqlite
Core Data
Client-Side storage
If you wish to go the web based route, I'd take a quick look at Safari Client-Side Storage and Offline Applications Programming Guide.
Basically, you store a local copy of the database in memory so incase the web service is down, users can still use the app.
So I have been doing lots of reading and found out NSCache is not persistent which is a slight problem for what I need to do. I have heard that I will need to use Core data instead... but I don't have any experience with core data so am wondering if its the only solution for persistent data.
The app will allow the user to search through a catalog, by typing in a search parameter in the code and select a distributor for their search parameter. What I want to do when the app loads is download the list of distributors and save them to a "cache" the will be persistent (till when the header I will make at some point changes and demands the app to update the cache), so that if the user turns the app of or the phone next time then open it the manufacture.
Now that I'm getting abit deeper into my app I'm getting abit lost in things for instance how would setting up a cache work with regards to NSURLConnection.
Any suggestions or code examples would be greatly appreciated..
This previous answer of mine might help you decide.
To sum it up:
If your data is small, static and low-complexity, use a collection class and write it to disk using the built-in class methods
If the data is static, low-complexity but large, SQL may be a good solution especially if you already know it.
If the data is dynamic and complex regardless of size, then Core Data is your best choice.
Viewed purely from the technical perspective, Core Data is always the best choice for iOS/MacOS API apps. Core Data is not just a persistence API, it is an API for creating the model layer of the Model-View-Controller design paradigm that the Apple API uses. It not only persist the data, but models it, validates its and provides an easy interface to the rest of the API.
If your going to be writing iOS apps, you need to eventually learn Core Data. However, it does have a learning curve and you should pick the method right now that will let you ship a usable app.
You can also check out sqlite. Here's another question that discusses getting started with sqlite on the phone: Where's the best SQLite 3 tutorial for iPhone-SDK?
The advantage to sqlite is that it is fairly easy to pick up. The downside is that you have to write queries for everything, and that can be a pain. It doesn't save objects, just data, numbers or text.
I've tried looking around but honestly not finding much help. I am mostly seeking for advice as to how I should approach to develop what I am thinking.
I want to accomplish something like this.
Imagine a website, with a backend database. This database contains information fed by users themselves. The website is fully functional, now I want users to be able to have the same functionality on their iPhones. I don't use a local database because I want all users to be able to have access to the same database, and this changes constantly.
What would be the best approach to:
Allow users to access all the information currently available on the website (database perspective).
Able to edit & add new entries to the database
I don't know if me creating an array to hold all this data would be wise to do. Specially with large amounts of data. I dont know how well it can scale.
Should I create a duplicate SQL lite database on the phone itself duplicating that of that website? What do you guys feel would be a good approach to this?
Comments, links, references would be greatly appreciated.
Thanks!
Sounds like the perfect time to create an API for your website. If the size of you application is not very big, you can use the same database, but would be good to run the API separated from the web server.
Essentially, such an API should allow you to make requests to certain URLs for retrieving, updating and deleting information from the database.
Depending on what server-side platform you are currently using, there are many options.
Client-side, your iPhone app can use http://restkit.org/ or http://allseeing-i.com/ASIHTTPRequest/ if you feel confident.