I have a project in which I have to store many images in each UIImageViewController. If user wants to add new image it will also store in UIImageViewController. For doing this according to me, I have to first create NSMutableArray and store UIImageViewController in it. Please Guide me if I should go with this logic or not.
It may well make sense to add an array to your controller (I'm assuming this is what you meant to type). Personally I'd hold the data in a more abstract class, say ImageRepository that holds the images (proably an array) and the controller references that to get the images (note this class would be the model, the M in MVC). This is especially useful if the same images to be added to each controller, just give each controller a same instance of the repo objects and adding/removing images only needs doing once.
Related
I have a view controller placeViewController which pulls in a bunch of Place objects, and from these loads and populates a matching bunch of PlaceView objects which are then displayed as subviews to its main view.
I need to update these views periodically which requires information from the model and other places to be pushed into the views
How should I properly structure this?
Keep an array of Place objects and give the model a PlaceView property to store pointers to the views
Keep an array of PlaceView objects and give the view a Place property to store pointers to the places
Keep both arrays and use a lot of indexOfObject objectAtIndex to jump between them
Some other way??
I need to update these views periodically which requires information
from the model and other places to be pushed into the views
You should really focus on an ObserverPattern. Yours views register to "notifications", and when changes are made, your registered views are notified.
http://en.wikipedia.org/wiki/Observer_pattern
You still can use NSNotificationCenter, but it will not futfill your needs since you need yours views make update per Place object (paired like a dictionary). So i recommend you to implement your own.
It will loose coupled because your controller will just only make glue between the observer and your views, and all the "logic" will be handled by the observer.
Well basvk got the answer in his comment but hasn't posted an actual answer for me to mark correct.
So here it is: "I would create a NSMutableArray with PlaceView objects. And the PlaceView class holds a #property Place *place"
I'm going through my code to make sure that all of my properties have the proper weak/strong modifier and I ran across this situation which I don't know what to do with. Keep in mind that I'm fairly new to iOS programming.
I have a normal MVC hierarchy where my controller creates an object called FieldManager. This FieldManager is used by my controller to dynamically create textfields. However, this FieldManager also needs to be used by the controller's model to periodically query the manager to find out information about the fields (such as is it required, should it's text be capitalized...etc).
So to summarize, I have a controller which creates an object that is used both by the controller and the controller's model. Therefore, I don't know if I should make the model's reference to FieldManager a weak property or the controller's reference to it a weak property. It seems that I should make both weak properties, otherwise FieldManager will get released. What should I do?
Thanks.
Things like that should belong to your model, so the way to go is to have a datasource.
Your controller asks the datasource to create and return the textfields, the datasource contacts the model and asks for a field manager for that model.
That's the way I would do it...
I'm starting a small project that displays circles having random radii, random color and random position on the screen. I want to implement this using the MVC paradigm in Objective C.
I have a class Circle that contains the following instance variables:
CGFloat radius
CGPoint center
UIColor radiusColor
This class doesn't contain methods, it just holds data. It is put in a separate file. (Circle.m & Circle.h)
I have a myModel class that is supposed to be the model for my MVC. It contains methods that randomly generate centers inside bound of my view, where the bound dimensions are requested from the View throughout the controller.
Every time a random property (that is center, color and radius) is generated, an instance of the Circle class is created within the myModel class, and stored in an NSMutableArray.
When the generation is done, this NSMutableArray is passed to the controller, which in turn passes it to the view, thus displaying the circles.
My question is that if I am to implement the MVC paradigm correctly, should :
The Model (myModel) hold instances of Circle, or the instances of Circle should be held by the controller?
My model be made of 1 class, or is it legal to be made of several classes?
The model know the bound size of the view or is that something that a violation in the MVC philosophy?
One last question. If I have made the implementation as I have stated above, are myModel and Circle separate models or both classes constitute one model?
Thank you!
[Should] The Model (myModel) hold instances of Circle, or the
instances of Circle should be held by the controller?
The model should hold the data. That's it's job. Imagine what would happen if you wanted to change the interface to your program. Instead of (or in addition to) drawing circles on the screen, you might want to display a list of circles and their locations. You'd might want to change or replace the view controller to do that, but you wouldn't need to change the model that stores the circles. Likewise, you might want to change the way that circles are generated, but keep displaying them the way you are now. In that case, you'd change the model, but the view controller and view could probably stay the same.
[Should] My model be made of 1 class, or is it legal to be made of several classes?
A data model is typically a whole graph of objects, very often of different types. You might have one object that manages the rest (although you don't have to). For example, your MyModel class contains an array that stores Circle objects. You could add Square objects, Group objects, etc.
[Should] The model know the bound size of the view or is that
something that a violation in the MVC philosophy?
The model shouldn't know specifically about the view, but it's fine for the view controller to tell it to produce circles within a given range of coordinates. That way, if the view changes size or orientation, the view controller will likely know about it, and it can in turn give the model new info.
If you have other components to your model than just circles, wrap everything in myModel. Even if you don't, you might still want to do so to allow for future additions.
Depends on your design. If you are writing a "document based" application (regardless of whether you are using UIDocument) you normally would have a single class that contains the others. Even if you aren't, having a single root class for archiving purposes, etc., is usually convenient.
The model should definitely not know anything about the view hierarchy. (Note that this is different from knowing something like "canvas size" - it would be legitimate to store such a property in the model, and let the view display the canvas however it wishes, such as in a UIScrollView.)
Btw, kudos for thinking about this ahead of time!
I have a question about Core Data. When starting my appliction, when is my data (which is stored automatically by Core Data) loaded into the NSArrayControllers? I want to modify it in the first place before the user can interact with it.
To be more specific: I have an NSArrayController for the entitity Playlist. Before the user can add new playlists or interact with the app at all, I want to modify the playlists programmatically. I tried windowControllerDidLoadNib: in my NSPersistentDocument (MyDocument.m) and awakeFromNib both in my NSPersistendDocument and the NSArrayController, but when I check in these methods with [[myArrayController arrangedObjects] count] I get 0 as result (the array controller's content is empty).
However, I actually have data stored and it is displayed to the user. I just do not know when and where I can modify it in the first place.
Thank your for any help.
Data is never "loaded" into the NSArrayController. The array controller is not an array itself. It does not contain or otherwise store data.
Instead, the array controller queries the object it is bound to for specific pieces of data only when that specific data is needed. This is especially true of Core Data in which managed objects are only fully instantiated when their attributes are accessed. The array controller moves data from an array type data structure to another object (usually an UI element.)
If you want to modify an existing store before it displays in the UI, you need to process the data before the array controller used by the UI is even initialized. If you're using NSPersistentDocument, then you can override readFromURL:ofType:error: to fetch and modify all your objects when the document is first opened. Alternatively, you can override the window controller's windowWillLoad or showWindow methods.
Regardless of where you do it, you must fetch all the managed objects you want to modify. You could programmatically create an array controller to do this but a fetch request is easier to micro manage if you have a large number of objects to modify.
You could try observing the "arrangedObjects" keypath of the controller and adding some logic to work that your array controller has been populated for the first time.
Another possible hook is implementing the awakeFromInsert/awakeFromFetch methods of your managed objects.
I have two very simple, identical UITableViews in my app that are populated with thumbnail images named "thumb1.jpg", "thumb2.jpg", etc. These thumbnails have associated original images "1.jpg" and text files "1.txt" used for image processing. Everything is stored in the app's Documents folder.
I want to keep the numbered, ordered naming for these files since it makes displaying the thumbnails in the UITableViews very easy with cellForRowAtIndexPath. I'm currently using a NSMutableArray (index: 1 object:"thumb1.jpg", etc) to track all images in the app.
The issue is that users can add/delete images so maintaining the order is important. For handling adding/deleting I'm looking at using insertObjectAtIndex and removeObjectAtIndex on the NSMutableArray, which will maintain order but will require programmatically changing image and text file names when this happens. For example, if there are five images in the array "0.jpg","1.jpg","2.jpg","3.jpg","4.jpg" and the user deletes the second image ("1.jpg") the array will now have "2.jpg" at index 1 so filenames will have to be changed to "1.jpg", "1.txt", and "thumb1.jpg".
How does this approach sound? I'm new to Objective-C so if you have other functions you'd use, etc I'd be interested to hear your opinion.
Renaming the actual image files themselves doesn't sound like a good idea.
I would implement 2 NSMutableArrays, one to hold the title/description of the image and one to hold the filename (or, if you wanted, the actual UIImage instead). Then if you need to delete, for example the item at index 2, deleting the same object from each of the two arrays will then leave them in sync.
If you start wanting more and more things to be stored for each row, I suggest you implement your own class. You can then implement an array of multiple instances of that class, and each class would have properties such as image, text, thumbnail etc. In fact, because you've already named three separate properties (main image, text and thumbnail) I'm tempted to say you should implement a custom class straight away.
Let me know if this makes sense or if you'd like some code to further illustrate it.