Central Data Source for all my View Controllers

So I have an app with a bunch (like 25+) vi开发者_C百科ew controllers. And these vc's use a lot of data, most of which I could either store locally in the app, or store it on my server. I would rather store this data on my server to minimize app size, so in order to do that, I read somewhere that the best practice for doing that is to have a data class, which would be a special class that gets all the data from the internet at one time in one place, rather than just getting the individual data as needed, in like viewDidLoad or somewhere similar. So my question is, is it really better to make a central data source within my app and every class draw from it. And if so, could you provide an example of how I should set up that class. For example, how to make it run in the background (I guess a different thread) and how to pass NSDictionarys and NSArrays, etc. from the data source to individual class as needed. Thanks in advance. I can clarify if necessary.

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You are talking about two different topics:

1. Accessing data from a main source from all the view controllers.
2. Accessing data from a server.

The best solution for you would be to create a new class that would hold variables that are used by some different classes. This tutorial explains how to do that - I think this would be one of the best solutions that you'll find on the internet.

For solving the second question, you should also create a class that execute SQLite statements and gets information from a database. You should use SQLite in order to do that, and if you won't like it, you could try to use Core Data, although SQLite in my opinion is much simpler. This tutorial describes how to do that.

After you've done both of the things you can create an instance of the class that handles the database services for you in the class that shares information between the view controllers, and access that instance from different view controllers.

In the end, you could try to perform tasks like that on different threads. You should try doing it using NSOperationQueue objects - they will do most of the job for you. I suggest reading about them in the developer documentation provided by Apple in order to understand how it works.

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Based on your replies in the comments, I would recommend this solution:

1. Transferring data from your server to the device - After downloading your data from your server, store it into an SQLite database in the device.
2. Accessing your data from your many view controllers - Use Core Data to access the downloaded data in your database from any of your view controllers.

If you don't know much about database programming, Core Data is an easy way to start. It encapsulates your tables into classes that you access like simple objective-c classes, so you don't have to learn SQL. You can also call them from any and all of your view controllers, whenever you need them, so you don't have to make a special class to handle your data. It is also better performance-wise and cleaner design-wise than passing your data through your view controller hierarchy. See the guide here.