在 VIewControllers 之间共享数据 - iOS

Question

For any object created I generally use two two scopes 1) Singleton 2) {local scope}. I am looking for something in between.

Say I have one object that 5 view controllers are editing. I want to share an object between view controllers without having to pass it between view controllers. But it should not also live throughout application since once I am done editing the object i don't need it anymore.

I don't want to inherit all view controller from another class an create a variable there. Since view controller are reusable for different objects. I want to create an object that comes to life before launch of first view controller, lives throughout the scope of 5 view controllers and then dies after I have saved it someway. Is there anyways I could do this in iOS.

Answer 1

An alternative is to use your AppDelegate. Within it you can declare a global var than 2 functions, a first one to get the current value and another one to set the value.

It might give something like this:

// Get AppDelegate instance
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate;

// Use your getter to get the current value
var something = appDelegate.getYourStuff();

// Or use a setter to set it, a modifier to modify oit
appDelegate.setYourStuff(yourStuff);
appDelegate.modifiyYourStuffAttribute(newAttributeValue); 

Don't realize if such a method is a bad practice or not, but it works for me.

Open to other suggestions!

Answer 2

As Mat said you can do is in that what. For me better is to create specific class for that that will do one particular job.

class EditingSession {
    class Factory {
        private static let session = EditingSession() //do it lazy
        static func create() -> EditingSession {
            return session
        }
    }

    func openSession() {

    }

    func endSession {

    }

    func getData () -> AnyObject {
        ...
    }
}

1. In editing session create private initializer. Factory should give the shared instance.

2. You can pass this class to your ViewControllers and manipulate with the data. You can inject it or just set as property in your VC or VM.

3. If you are done with editing you should end session and clear data or other stuff.