I'm pretty new to the whole coding scene and was trying to create a way of accessing similar methods from anywhere within my app. I created a class called HelperMethods : NSObject. I then defined all my helper methods like this: + (returnObject *) thisIsMyHelperMethodWithParameter:(object*)object; and then created the method body in the implementation. I then put an #import "HelperMethods.h" in my app prefix file so I can access it wherever I like in the app. I then call [HelperMethod thisIsMyHelperMethodWithParameter:]; from anywhere within the app. It works fine and I haven't had any problem, but is this a legitimate way of creating a central hub for useful methods?
Thanks,
Mike
Well better if you want to create the class which work as a central hub then create the singleton class and access anywhere fron the other class. The advantage of creating singleton class is that it shared single memory space. So that it will be less overhead, when accessed the methods and variable from other class.
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 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.
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.
So I'm getting myself into a confusion over where my data's going and where it's stored in my application. It's not a specific question so hopefully someone can provide a generalised answer.
I need to pass some data around between a few UIViewController instances, and I'm currently doing that with a singleton object called my dataManager. This class has one method, a class method, called + (LCDataManager *) sharedDataManager, and that method basically checks if whether the sharedDataManager already exists, if so, return it, if not, create it and set up its variables. This means that I can refer to that class anywhere I like, access and modify its variables anywhere I like, from across multiple classes.
First question: is this the correct / best / most appropriate means of passing data around like this? I'm hoping it obeys MVC, it feels like it does, and I hope I'm right.
Second question: what if I want to put an instance method in that class, and call it from within the class method? Let's say my sharedDataManager needs to call a method to grab some objects one of its variables (an array), and put them in another array, then send that back out again. I can't do that, can I? What's the way around that? If I make an instance of that class (rather than using the shared instance), I lose the ability to use that instance across multiple viewControllers.
I'm hideously confused, and it seems like it's not the problem I'm making it. Appreciate any guidance, and preferably not that "Read the Apple documentation" stuff – they write as if you already know what you're doing, and frankly I don't yet.
First question: is this the correct / best / most appropriate means of passing data around like this? I'm hoping it obeys MVC, it feels like it does, and I hope I'm right.
Your design is perfectly MVC compliant.
Second question: what if I want to put an instance method in that class, and call it from within the class method?
you can surely define an instance method and call it like this:
[[MyModelClass sharedModel] myInstanceMethod];
indeed, [MyModelClass sharedModel] will give you an instance of MyModelClass (which should be guaranted to be unique being it a singleton).
If you want to call the instance method from the sharedModel class method, you could also do that, because sharedModel owns a reference to your singleton, so it can send messages to it.
is this the correct / best / most appropriate means of passing data around like this?
There's nothing wrong with only having a single instance of LCDataManager, but using the Singleton pattern has potential problems. An alternative is to just initialize one LCDataManger and to pass it around to wherever it's needed.
what if I want to put an instance method in that class, and call it from within the class method?
The accessor + (LCDataManager *) sharedDataManager should only return the instance. I guess what you want is something like
+ (LCDataManager *)preparedDataManager {
LCDataManager *shared = [self sharedDataManager];
[shared doSomeInstanceMagic];
return shared;
}
- (void)doSomeInstanceMagic {
// magic!
// grab some objects one of its variables (an array),
// and put them in another array
}
Matthijs Hollemans has an excellent three-part tutorial on his blog about the correct way to make your view controllers talk to each other:
Part 1
Part 2
Part 3
there is no problem with this development architecture, and it is the must used (I think) in the iOS development. In the book IOS Programming: The Big Nerd Ranch Guide they call it Model View Controller Store.
Regarding your second question, yes, you can declare instance methods and call then from your sharedDataManager. What is not usual is creating other instances of a singleton class, but it is possible.
Is ok if I add class methods that I need over all my project in the application delegate?
and then I import the delegate in the current UIViewController and I invoke the method: [MyAppDelegate classMethod];
Is a good approach ?
thanks
I set up an APP_DELEGATE macro that is defined as:
#define APP_DELEGATE ((AppDelegate *)[[UIApplication sharedApplication] delegate])
... so when I need to use it, I just code:
[APP_DELEGATE someInstanceMethod];
So yes, I use instance methods instead (for simplicity). Just define this macro in your AppDelegate.h and include it wherever you need it.
I think it should be fine, but I would only do it if it a) makes sense, and b) is truly the only place for that method. I'd think long and hard about whether that functionality belongs in the delegate or in some other singleton or shared class.
I would say that it's an acceptable approach but I would not recommend it. It depends on what the methods you are taking about do. For example, if you want to be able to access your data model from everywhere in your app, it's better to use a singleton, so that you separate the model completely from the rest of the app.
it's depending upon ur app needs or context.
if u r going to access class variables then u can choose class methods to create.
but u cannot access the instance variables.
but my choice is instance method which will operate on both class variable and instance variable.
The difference between class methods and instance methods are
Class methods
Operate on Class variables (they can not access instance variables)
Do not require an object to be instantiated to be applied
Sometimes can be a code smell (some people who are new to OOP use as a crutch to do Structured Programming in an OO enviroment)
Instance methods
Operate on instances variables and class variables
Must have an instanciated object to operate on