I am new in iphone development and i needed a array which i use to access in different class so my senior told me that you should declare in App delegate and access it another class in which it require, so i wrote line for that
MyAppAppDelegate * appObject =
(MyAppAppDelegate*)[[UIApplication sharedApplication]delegate];
I done my task successfully but i couldn't get it 100%. Someone tell that why we use this and in what exactly situation in which we've to use this?
AppDelegate is loaded first when you run your application as it contains window. So, the variable and objects you want to access throughout your project is declared in AppDelegate. You just have to create an instance and you can access all the objects in AppDelegate.
ApplicationDelegate can be useful as a singleton class but you have to use it with discretion - and there are varying opinions on this - but if you have a few global type properties or methods you want to recall from various other classes, and I emphasize few, then ApplicationDelegate may be a nice place to add these.
And yes, it is bad design - but you can get away with it if you are prudent and as #Sedate Alien mentions, take a look at dependency injection.
The purpose of ApplicationDelegate, by the way, is mainly to handle events like loading your application, when you return to home screen, when you come back from home screen, etc.
Related
First of all, Sorry. I'm not good at English.
Hi. I'm beginner of iOS.
To learn Objective-c for the first time
Define the class name and method name in the header file and declare the class object created above in the main.m file on implementation details. M calling the method does.
[NewPoint SetPoint: 3];
[NewPoint print];
But iOS studied, I suddenly was wondering iOS studied.
Without calling the method directly from the main.m, appdelegate.m method override you if you do not like this [NewPoint SetPoint:3] that is the exact reason why I wonder.
Why Running just override method not using [NewPoint SetPoint:3] like this.
For learning purpose it was taught to create class in main.m itself.
But in real programming world, you follow classes which are a blue print, so these are created separately for full use throughout the application and other classes/objects are able to use them.
Classes make your code separate from different classes. AppDelegate is one such class which comes initially with a project.
Later on you will make your own classes like Person, Employee, Box etc each one having their own properties, behaviours etc.
What I feel is in your training you were taught to create a class and object as NewPoint, later it was created in AppDelegate. Now you can try to use a differenct class called NewPoint and make an object of that inside AppDelegate and use it.
I did something a little bit nasty today.
All of our view controllers inherit from two different parent view controllers, let's say XXXViewController and YYYViewController. XXXViewController in turn inherits from TrackedUIViewController, which is a class provided in the Google Analytics SDK so all your view controllers can inherit from it and easily track them.
YYYViewController however, inherits from a different type of view controller. Ah, and it's an open sourced piece of code that I really don't want to change.
What's the problem here? We cannot track any of the YYYViewController children because we can't access the methods provided in TrackedViewController, since they are private.
I don't want to modify the source provided in the Google Analytics SDK. So what did I do? Create a category that exposes those methods, just to avoid the compilation error.
The obvious downside to this is that the GA source code changes it may break, but it will be fairly easy to detect.
I was wondering what other problems I could be facing by doing this, and if you guys can think of a better approach.
Thank you
You can go up in the inheritance chain of YYYViewController, see in turn what class it inherits from. If it's UIViewController, simply change that particular superclass to TrackedUIViewController in the source and you're fine to go.
Example for better understanding: suppose YYYViewController inherits from ZZZViewController, which in turn inherits from UIViewController. Now you can change the superclass of ZZZViewController from UIViewController to TrackedUIViewController - since TrackedUIViewController inherits from UIViewController, no functionality will be lost, but magically your whole YYYViewController class will become trackable.
Hope this helps :-)
You already mentioned the biggest risk of using undocumented APIs: Changes to the API are beyond your control and may break your logic, for example if methods are removed/renamed, or their behavior stops matching your expectations.
From the purely technical point of view, I can see no further problems, since in Objective-C all methods are public. As long as they continue to exist, you may continue to call them.
I would say the root problem is excessive subclassing. Keep view controller hierarchies shallow. Use composition instead of subclassing. If you must subclass ensure that functionality that a class provides can be turned on & off by it's subclasses.
I'm aware of other posts on this topic but I'm only really one rung up the ladder from being a noob so need a bit more help.
My iPhone app has several global variables - some I have declared and given values in a class but others need to be set during a login process (like a token for example) that then need to be accessible for the lifecycle of the app from any class or method. I am told I should really be using a Singleton object for all of this which I presume is a class that's instantiated on startup. If so, could someone give me the simplest example of such header and implementation file and how/where I should instantiate it? Then I need to have some strings that are set from the off and others that can be set/got later on?
Thanks very much in advance. Also, I'm new here so if my etiquette is off in any way, please let me know.
Thanks,
This link shows some code to create a singleton class : http://www.galloway.me.uk/tutorials/singleton-classes/
You would use it something like :
[[MyManager sharedManager] doSomething];
The call to sharedManager would get the one instance of the class (or, if this is the first time you called it, would create it) - this makes sure that you only have one of them :)
It also overrides release, retain, autorelease etc to make sure that you can't accidentally get rid of the sharedManager by mistake!
This class will instantiate itself the first time you use it but if you need it to be created on startup, just call [MyManager sharedManager] and it will create it for you.
You define the class like any other objective-c class - just add properties etc
Hope that helps :)
Global variables aren't good, but singletons aren't much better when they're just used to provide global access to some data. Anything bad you can say about a global variable, you can also say about a singleton that's used for global access. A better solution is to create a data model and pass that model from one view controller to the next.
Here's a previous SO question that might help.
I've run into a little problem while developing a Core Data driven Quiz and be a bit confused about a best practice to solve my problem.
I have approximately five templates for the different questions, which will be loaded in case which question is displayed. So I check which template has question 1 and push the new question-template view into my navigation controller. Because its always the same code I want to write a function (I came from php) which gets the next question-id as argument and decide which template will be loaded and push the next view into the navigation-controller.
What is the best practice to solve this problem? Can I write a function with access to the navigation-controller, and my Core Data classes. And if yes where I have to create this function?
Okay I think I found an way but gets here another Error. I create a class called QuestionRouter and define an class method. I'll import this class into each viewController where it needed. The class method gets the correct template from Core Data without an problem. But now I wan't to load the correct view. For that I need to access the navigationController defined in my AppDelegate.
So how I can access the navigationController in my AppDelegate for another class?
Hope for an answer.
Mister-D
I'm a beginner with Eclipse RCP and I'm trying to build an application for myself to give it a go. I'm confused about how one actually goes about handling model objects. None of the examples I can find deal with the problem I'm having, so I suspect I'm going about it the wrong way.
Say I need to initialise the application with a class that holds authenticated user info. I used my WorkbenchWindowAdvisor (wrong place?) to perform some initialisation (e.g. authentication) to decide what view to show. Once that's done, a view is shown. Now, that view also needs access to the user info I had earlier retrieved/produced.
The question is, how is that view supposed to get that data? The view is wired up in the plugin.xml. I don't see any way I can give the data to the view. So I assume the view has to retrieve it somehow. But what's the proper place for it to retrieve it from? I thought of putting static variables in the IApplication implementation, but that felt wrong. Any advice or pointers much appreciated. Thanks.
The problem you are facing here is in my opinion not RCP related. Its more an architectural problem. Your view is wired with business logicand!
The solution can be done by two (common) design-patterns:
Model-View-Controler (MVC)
Model-View-Presenter (MVP)
You can find plenty information about this in the web. I am going to point a possible solution for your particular problem using MVP.
You will need to create several projects. One is of course an RCP plugin, lets call it rcp.view. Now you create another one, which doesnt make UI contributions (only org.eclipse.core.runtime to start with) and call it rcp.presenter. To simplify things, this plugin will also be the model for now.
Next steps:
Add the rcp.presenter to the
dependencies of rcp.view (its
important that the presenter has no
reference to the view)
Export all packages that you are
going to create in the rcp.presenter
so they are visible
In rcp.presenter create an interface
IPerspective that has some methods
like (showLogiDialog(), showAdministratorViews(User user), showStandardViews(User user))
Create a class PerspectivePresenter that takes IPerspective in the constructor and saves it in an attribute
In rcp.view go to your Perspective, implement your interface IPerspective, and in the constructor create a new reference presenter = new PerspectivePresenter(this)
call presenter.load() and implenent
this in the presenter maybe like this
code:
public void load()
{
User user = view.showLoginDialog(); // returns a user with the provided name/pw
user.login(); // login to system/database
if(user.isAdministrator())
view.showAdministratorViews(user);
else
view.showStandardViews(user);
}
As you can see, the view just creates a reference to the presenter, which is responsible for all the business logic, and the presenter tells the view what to display. So in your Perspective you implement those interface functions and in each one you can set up your Perspective in a different way.
For each View it goes in the same way, you will need a presenter for the view which performs operations and tells the view (using the interface) what to display and passing down the final data. The view doesnt care about the logic. This is also very usefull when using JFace-Databindings (then only bound data is passed to the view).
For example, the WorkbenchWindowAdisor will just create everything that is needed in the application. Other views, perspectives, then can enable/disable menus and so on depending on the data they got (like when isAdministrator you might want to enable an special adminMenu).
I know this is quite a heavy approach, but the Eclipse RCP is designed for big (as the name says rich) applications. So you should spend some time in the right architecture. My first RCP app was like you described...I never knew where to store things and how to handle all the references. At my work I learned about MVP (and I am still learning). It takes a while to understand the concept but its worth it.
You might want to look at my second post at this question to get another idea on how you could structure your plugins.