I came from Android background and I'm new to Swift.
I want to know how to use common functions in ViewControllers with DRY principles.
I need all of my ViewControllers to call following functions from one place:
isNetworkAvailable() //check app has internet return boolean
getLoggedinUser() //return logged in user object which I set before
showAlert(message:String) //display a popup
startLoader() // display a loader
stopLoader() // stop loader
As you can see these methods are global and I need to reuse them many times. So I don't want to copy paste the same code over and over again.
In Android I simply make one BaseActivity and put all those methods in it. Later I will extend the BaseActivity into SubActivities and inherit those common methods.
I'm not sure how to do this in "IOS Swift" as all the ViewControllers are attached to StoryBoard.
Can you please tell me what is the best way to achieve this? How does professional Swift developers handle situations like this?
(Please note - I don't want to delete story board and manually create UI elements.)
Thanks in Advance!
Create a CommonFunctions named public class (just a suggestion you can name it any class name which you want) extend it from NSObject and import UIKit Module in it because I think you also want to perform UI Operations in it like startLoader() & stopLoader() then you can write static global methods which you are mentioned in your question.
You can call then using CommonFunctions.methodName().
Or if you don't want to make static functions then create object of CommonFunctions class wherever you want to access those global methods and call the method which you want.
Related
I am working with a objective-C framework.
I have a public framework header "MyPublicHeader.h" exposed to the client application. I have a custom class in the project,
//MyCustomClass.h file
#interface MyCustomClass.h
- (NSString *) methodA;
#end
//MyCustomClass.m file
#inplementation
- (NSString *) methodA {
}
#end
If I want the client to instantiate the class I have to make it as public framework header. I want to hide the interface as a curiosity, is there any way to do it???
First know that nothing can be truely hidden in Objective-C due to the nature of dynamic dispatch and the features in the runtime which allow discovery of methods etc.
That said there are a number of ways to do this, a couple:
Use a subclass. Declare a superclass and publish its interface as part of your framework. Make your class a subclass of this and publish its interface only within the framework. You define one or more init methods in the superclass which return and instance of the subclass, and if you want to expose any further API define it in the superclass with dummy (or faulting) implementations and less the subclass override etc. This approach is similar to the model used for classes like NSString.
A .h file is just text and you can exploit this: make two .h files, say MyCustomClass.h and InternalMyCustomClass.h. In the first just declare the interface with no members, or the API you wish to make public, and publish that to users of the framework. In the second declare the real interface used within the framework. You must make sure to keep all three of the files (2 .h, .m) in sync. This approach would be call little naughty by some, "here be dragons" by others, or "needs must" by yet others...
You might also like to look into "class extensions" which are related to categories.
Hope that satiates your curiosity a little, and keep up with the curiosity its good (except for cats)!
You could create an empty wrapper class which only holds a reference to your MyCustomClass object.
When they create this object you secretly instantiate an object of your MyCustomClass inside and extract it when they pass you an object of the wrapper class.
Not sure if this is exactly what you want to achieve, but could be a workaround.
I am adding functionality to an AWS class that creates a singleton (AWSIdentityManager) and the code for that class is in flux (AWS are improving it). I would like to make my added functionality more distinct from the AWS code so that I don't have to keep changing it when they upgrade.
Can I achieve this by subclassing or extension?
My goal is not to create another copy of the existing singleton, I just want to add methods (and hopefully properties) to it, without making too many changes in the released code.
I should note the following: The original class is written in Obj-C. I would like to have properties if possible.
To extend
extension AWSclass {
func functionA () { ...}
}
usage
AWSclass.shared.functionA()
I have a class, User, that has an NSMutableArray that stores custom NSObjects. I only want one of these to ever be instantiated throughout the entire app, and I would like to be able to call methods on it in each ViewController for getting and setting. My problem is that I don't know how to call the methods so they apply to this one instance, instead of creating a new one each time. I'm new to objective-c, so the learning curve makes me feel I'm missing something a bit obvious. I've been working on this all day and am at a wit's end. Is there a good solution to my dilemma? Should I use a singleton class?
(If it helps, the class User is basically a class that stores a to-do list for each user that uses my app. The custom NSObjects are to-do items. There's probably a better storage method that should be used here, but I'm not sure what it is.)
RandomPleb it sounds like what you're looking for is a Singleton. http://en.wikipedia.org/wiki/Singleton_pattern. I also think this question has been answered before so search around on SO.
Laymen's terms; you create a static reference to the class that you only want one of inside that class, then make a static method in the following way:
//call this from classes that want to modify it
public static getsharedinstance()
{
if(the static instance of this class does not exist){
instantiate instance;
}
return this classes static instance..
}
Hope this helps (and if this is wrong, I hope someone can correct me)
Also in regards to your storing objects, I think NSMutableArray is fine unless it is a very big persistent list where each task has many properties in which case maybe using CoreData would be better.
Fenix
I have a theoretical-practical question. I can't understand how I must do. I have a class let's call them DataManager that manage all plist writing-reading things and I need to get access to plist (i.e. work with that DataManager class) from different UIViewControllers.
I also have one class, I call it ModelManager, that is work with all kind of "utilities classes", include my DataManager. ModelManager works only with one complex UIViewController right now, let's call it MainUIViewController for clearness. And for now, I thought that all calls from UIViewControllers will be comes to ModelManager and from it to end-call classes. But now I'm confused.
Here is an illustration of my architecture:
I'm see different approaches and don't know how to decide and if there is some rules or guides for that. So, here is my choices:
1) I add some interface to ModelManager and from my another UIViewController (not a MainUIViewController) allocate and initialise it.
2) I add some interface to ModelManager and create a property with reference to ModelManager in another UIViewController and when segues performs set this property from MainUIViewController.
3) Work with DataManager itself and allocate and initialise it from another UIViewController
4) Work with DataManager itself and create a property with reference to DataManager in another UIViewController and when segues performs set this property from MainUIViewController.
Which approach is correct?
I know that this is some kind of depends from developer which approach to choose, but I never read and didn't find any tutorial or guide of how to develop multi-class architecture.
Ask me about any circumstance that you want to know.
You can use a singleton or you can instantiate one instance of the class in your app delegate and pass it around to all your view controllers via #propertys on each controller. There's no right answer, it's mostly a matter of preference. I prefer to make my ModelManager/DataManager type classes singletons, but a lot of people are rabidly opposed to singletons. However, if you work with Cocoa for any length of time you'll find that it's full of them (NSUserDefaults, NSFileManager, UIDevice, probably some others I'm forgetting).
Here's a good example on how to create singletons: http://www.galloway.me.uk/tutorials/singleton-classes/
BTW: Once you have your singleton, learn how to use KVO to make your view controllers respond to changes in the model. It's pretty fantastic once you get the hang of it. http://nshipster.com/key-value-observing/
I have class called ViewController. How to make this class is a sub-class of "metaiosdkViewController" and "JWslideViewController". Help me with syntax.
i have written like this
#interface ViewController : MetaioSDKViewController,JWslideViewController
but this giving me error
objective-c doesn't support multiple inheritance,but if you want to add some extra behaviour you can achieve it through delegates..
yes objective-c doesnt support multiple inheritance but you can give one parent so
#interface ViewController : MetaioSDKViewController
and
#interface MetaioSDKViewController : JWslideViewController
this is just an idea I know you can implement well as per your need
What is it that you want to achieve with multiple inheritance?
Do you want to override methods from each of these super classes?
Note that objective c provides 2 mechanisms for extensibility:
1) Implementing a Protocol and make your object the delegate:
#interface ViewController : <MetaioSDKViewController,JWslideViewController>
This enforces ViewController to implement certain methods as defined in contract by 2 delegates, and at some point in processing, they get called. If you don't implement them, they may simply not be called but you may not get desired functionality.
Example: UITableViewDataSource protocol that defines many methods that UITableViewController subclass implements. cellForRowAtindexPath is very famous example of a delegate method that your own table view subclass must implement to draw your own custom cells.
Note that this is not the type of extensibility that subclasses provide in general sense. Your class does not extend any functionality here. Rather it becomes what it says - a delegate - someone who is assigned to do some task. Like you do:
yourTableView.delegate = self; //tell self to be the delegate of yourTableview
Library code does it's stuff and in some point in processing it calls [delegate someMethod]. If your own class implements it, it calls it, otherwise delegate will be nil, and it may just be NO-OP and you don't get desired functionality. Again, this is implementation-dependent. Maybe the protocol defines that the method is compulsory, in which case your class MUST implement this method in order to compile.
2) Implement a category:
This is sort of a shortcut way to extend library classes. They act like an extra stub which, when your code runs, attaches itself to the already existing memory layout of the library objects and provides extra functionality.
You can define a category on any of the in-built classes as well. In fact that is the primary objective it is used for. For example, here is an NSString category which provides HTML conversion. There are hundreds of categories implemented as open source and they provide enormous benefits where library code falls short. Discussing their suitability in entirety is however out of scope for this discussion.
One thing to note however is: You do not override anything using a category. Rather you are supplying something in extra. For example if you want some custom drawing across all your app views, you can define a category on UIView in your project and then all your views could simply include the category header file. You don't even have to inherit from this category, you simply inherit from the base type.
e.g. in the NSString category example above, you do not have to define your NSString to be of type NSString+HTML. Instead you just include the responsible NSString+HTML.h file wherever you want those extra methods like stringByConvertingHTMLToPlainText and so on. The changes remain limited to your project - to the files where you include this category.
Categories do not provide for extra data members - and that is something that only inheritance can provide. Yet, multiple inheritance among viewcontrollers is something you should definitely reconsider hundred times - you will see that what you are looking for is not multiple inheritance.