I am new to the world of iOS development and Swift, and have run into a problem. When my app starts, it is to connect to a web service, and download a JSON string containing information for "posts", then, it should load the first post into the first view. After that, the user can swipe left or right to load a new view with the next post. I figured that I could use something like this to do that:
let nextView:ViewControllerName = ViewControllerName();
self.presentViewController(nextView, animated: true, completion: nil)
However, this infers that I already have another UIViewController created and ready, but since I am dynamically loading data, I will have to create new views on demand and create an indefinite number of them.
How, then, can I create a new UIViewController, add controls to it, add controls (including custom controls), and populate the controls with data all in Swift code? Could I somehow integrate it with storyboards?
You could have one UIViewController which contains a paging scroll view (UIScrollView) that contains the views to be displayed.
When the user swipes, you just populate the view to be displayed with the appropriate data. A common pattern is to have 3 views in the scroll view with the next and previous ones already preloaded.
Trasform your JSON response into an array of UIViewControllers (factory pattern). For each item you can create something like - (UIViewController *)viewControllerFromObject:(MyObject) object
Install ISScrollViewPageSwift
Integrate it
Search for "UIPageViewController" tutorials. You could also use a third party library like "iCarousel" which makes it a little bit easier.
https://github.com/nicklockwood/iCarousel
But: creating a new view dynamically on demand asynchronously over the network will create a very poor user experience. On iOS the everyone is used to a very fast and fluid user experience - as soon as the user swipes he wants to see immediately the next view. But a network request takes 0.5 seconds - 10.0 seconds, depending on you network connection. It would be better if you preload some pages to have them already in memory. And as soon as the user has viewed some of the preloaded pages you can preload more of them... and so on... indefinitely.
Related
So I was trying to create a sample ios application. As I am designing the app UI with the storyboard (and not coding), I find Xcode really hard to understand.
what I want to do is I added a scrollView to the view controller. now what I want to do in the scrollView is simple.
I want my scrollView to have buttons (vertically stacked) and it does some action on the basis of the data it is getting from the database. let's suppose it is getting links from the database and on a click of those buttons those links open. now the data may contain 10 links, or 20 links .. basically, we want it to be according to the database.
now if I was designing the UI programmatically it would look something like
ScrollView{
for loop...{
button("for example name coming from the database"
}
}
or atleast this is what I know of.
so how to do the same with storyboard ?
like we first take it's refernce to the uiViewController class.. and then ?
You need to add buttons programmatically if they are created dynamically depending on external non static data. Create new UIViewContoroller class and implement it with connecting storyboard file, the easiest would be to add buttons inside some kind of UIStackView which is inside scrollview imo, or by using UITableView if there are significant number of links to display.
I am attempting to build an application in swift that is essentially a book and some pages of this book allow for user input that is stored in the application.
I am new to swift and am unsure of the best way to approach this problem. So far I have tried using a Page View Controller and separate View Controllers corresponding to each page. The Page View Controller class navigates through the pages using Storyboard IDs to instantiate the View Controllers in an array. This works in creating a navigable book but I run into issues when trying to create outlets from the text fields on some pages since essentially the View Controller is instantiated each time its accessed and so it does not permanently exist.
I am totally and utterly lost as to where I should go from here. Any advice/wisdom will be deeply appreciated.
Thank you
simplest Approach is Collection-view with pagingnation(self.collectionView.pagingEnabled = YES).
https://medium.com/#shaibalassiano/tutorial-horizontal-uicollectionview-with-paging-9421b479ee94
create multiple cell one for your Page(reading) and second for input field.
it also helps for memory management. because cell are reusable. and cell that are visible to Screen are only loaded in memory.
you can also Create Custom layout for animation as per your requirement.
What is the best way to have multiple UIViewControllers that can be accessed from a side menu and without having to re-download any data each time the view controller is shown?
Say for example I have three view controllers, one is a homepage that shows recent notifications, one is a news page that shows recent articles and one is a page that has a collection of images. When each view controller is loaded, data is downloaded from a remote server and displayed - if the user switches to another view controller and back again I want the previously downloaded data to be shown immediately without having to be re-downloaded (until a UIRefreshControl is used or similar).
Off the top of my head I can see this being achieved in 4 ways:
Store the data in a singleton and load the data from this if it has been previously downloaded, however, this seems to go against general practices that I have seen and also doesn't seem efficient - especially if there is a lot of data and/or multiple view controller.
Use a UITabBarController that selects the index based on the side menu instead of the traditional bottom bar, would this cause issues if there were 10-12 items on the side menu?
Cache the data to disk (using NSCache etc) and instantiate/dismiss each view controller as needed, the view controller can use the cached data - only one view controller will exist in memory at a time.
Use some kind of customised container view that caches the view controllers and loads them as they are needed, feels a bit hacky and not very efficient?
What are the best ways to achieve this? Most tutorials I see just show how to segue/present view controllers but I have struggled to find anything that explains how to preserve the data that was downloaded on them.
Just as an FYI. If one of your ViewControllers is supposed to "show recent notifications/articles" then caching data won't work because it might not be the most recent unless you pull from the server every time. (Unless the recents are getting pushed and even then you might have huge sync issues if you don't pull every time.)
That said, you options 1 and 3 are effectively the same, the only difference is where you are keeping the information.
You should not be using a tab bar controller. If you can't use UISplitViewController then you should make your own custom container view controller.
As for the caching issue. I would implement some sort of caching mechanism for each endpoint. It could store in ram or on disk but I think in ram is better because the data sounds pretty volatile.
Set it up so that when a view controller makes a "network" call, the function it uses calls the closure with the last data it pulled and then optionally can make the network call again and call the closure a second time with the new data. This way the VCs will be very responsive in getting data up ASAP and still pull in the new data on every view will appear.
I would go with a combination of option 3 and 4.
There are many formats you could use to cache the data to disk. You could use a database like CoreData or Realm, or write directly to files as a Plist, JSON, NSKeyedArchive.
You probably should build a container view controller as well. Thats what a TabBarController is after all. It's pretty easy to do and the docs cover what you need to do. This will make you app more efficient by only having to load data from the database/file the first tome you go to the view controller. Then when switching sections, it can just show the VC thats already been loaded.
I am building an app which mainly shows a tableview. In this tableview I have some custom table rows. The table rows are filled with data received from the server. I receive multiple kinds of data from the server. I will store it in arrays.
For example, I've got three kinds of arrays. Each is filled with different kinds of data received from the server. See below:
(NSArray*)carList_
(NSArray*)motorcycleList_
(NSArray*)bicycleList_
The actual program that I've got now, only shows the carList in the tableview. Foreach car in carList, there is a table row.
The thing that I've in mind to do is a little bit tricky. I want to add a tabbar at the bottom of the screen with three buttons. When I press the first button, I want the table to be filled with the carList. When I press the second button, I want to fill the table with the motorcycleList. And when I press the third button, I want to fill the table with the bicycleList.
As you can see, I will use the same tableview. I will only refill it with the data I want to see. Is this allowed in iOS? Cause I read something about that the tabbar is for multiple views, and I only want to use it for changing the data in my table. Only the fourth button I've planned for future development will open a new view. If it is not allowed, what is a good alternative do do it? Buttons maybe? I searched the web for what I want to do, but it seems that my idea has never been used before, I think my idea is not allowed in iOS.
At this moment I've a initialViewController (with almost no code cause it is used only to initialize some things of the server. It acts like a splash screen) and I've got a rootViewController which does the works. In the rootViewController I've got my Table with Table rows and it has the different arrays of data which are retrieved by a method that is called when the rootViewController is loaded.
I am programming without Storyboards, because I'd like coding and I want to understand how it works 'underground'. What is a good way to implement the tabbar if it is allowed what I want to do with it? I don't think a standard tab controller will work, because I am working with only one view.
Of course you can use the UITabBar solution. However this might be not very useful and this is not the idea behind the UITabBar. You can instantiate the same TableViewController vor each tab. In this case you can use the same class but you have up to the instances of this class when the user cycles through the tabs. This will be obvisously a waste of memory.
Your descriptions sounds like a UIToolBar with a UISegmetenControl in it might fit your needs better. You can also place it at the bottom of the screen and you will need just one TableViewController for your data.
UISegmentedControl is designed for switching between different data representations. It is also commonly used for switching between table datasources. But it often appears at the top of a view. Take a look at Top Charts tab of App Store app.
Tab bar is designed to present different views for each tab. Here are progress steps to achieve your result:
Use different instances of table view controller for each tab
Configure each instance for displaying one particular array, depending on tab position
Keep arrays in external (outside table view controller) storage, instances should have an access to it
It's better to preload data, while user is examining an active tab. Hence, load data outside of table view controllers, possibly in AppDelegate. Use notifications to update table view when data are available.
I'm new to obj-c/iOS and I'm having trouble understanding conceptually at least viewControllers. I've read a lot of the Apple Doc's, I've even used viewControllers to some extent in xCode, but I still don't quite get what they are, or what are the best ways to use them.
I've been an AS3 dev for many years so my mind works in the context of MovieClips/Sprites and the Display list to get graphics on the screen.
Ok so from my understanding...
A viewController is a kind of class that handles graphics in some
fashion and then allows you to do something with them?? What is it in it's most basic sense?
You seem to add viewControllers to a Window class, which I guess is a bit like
adding a display Object to the Display list?
What is it that a viewController does for you in it's most basic sense?
Are there certain things you definitely can't do with them or shouldn't do
with them?
Do viewControllers need to be connected in some way to the rest of the iOS framework to function (apart from being added to a window).
How exactly do they use data? (I've read up on MVC, I understand that conceptually this is a slightly different question) as I understand it you don't hardcode data into a viewController, so how does a viewController access any static data?
Let's say I just wanted to throw an image up on the screen, exactly what part would the viewController play in that process? is it just something which handles only one small aspect of that process or is it the whole show and handles everything?
Does one viewController handle multiple images? is it like it's term, a "controller" for all the images presented on screen, or does it handle one image at a time?
What is a viewControllers connection to the image(s) it handles? it contains references to them?
I'm using the Sparrow framework which is helping but I would still like to be able to get my head around what viewControllers are so I know how to use them properly.
Ha, I apologise for the above I know it must look like I'm completely confused :) thanks for any advice.
Hope this helps you:
A viewController is a kind of class that handles graphics in some fashion and then allows you to do something with them??
It's the glue between a View (Xib File) and the Data (Could be
CoreData or whatever you're using in the backend). All the UI Elements
you are using in the View you normally define as properties in the
controller to get access to them.
What is it in it's most basic sense?
You seem to add viewControllers to a Window class, which I guess is a bit like adding a display Object to the Display list?
I don't really know AS3 so I cannot compare Display lists with ViewControllers. But basically ViewControllers are there to handle
different types of transitions between the views and accessing
(setting/reading) the data which is displayed in the view.
What is it that a viewController does for you in it's most basic sense?
Like I've written above. Most basic sense they interpret what the user
does on the view and depending on the action of the user changes the
model.
Are there certain things you definitely can't do with them or shouldn't do with them?
It is always hard to keep the border between model and controller.
They are pretty close to each other. So what I normally try is to
delocate all logic stuff (like calculations, database access and so
on) this does more belong into the model part. But of couse you're
using these external classes in the controller.
Do viewControllers need to be connected in some way to the rest of the iOS framework to function (apart from being added to a window).
Well like you already have written the ViewController needs to be
connected to a view. Otherwise it would not make much sense. There are
different subtypes of UIViewController such as UINavigationController
where you probably need to overwrite some other methods to provide the
whole functionality wanted by these special subtypes.
How exactly do they use data? (I've read up on MVC, I understand that conceptually this is a slightly different question) as I understand it you don't hardcode data into a viewController, so how does a viewController access any static data?
There could be different approaches to store the data. Simplest way
would be to have the data directly stored in the UIViewController.
This could be a custom class which is the container of the data. All
changes are directly written into this class and displayed by the
UIViewController. But in most of the cases it makes sense to use
CoreData (Which is responsible for reading/writing the data into a
sqlite database). You could look at CoreData as your model and the
UIViewController gets the data from there and passes the data which
the UIViewController has received from the View back to it.
Let's say I just wanted to throw an image up on the screen, exactly what part would the viewController play in that process? is it just something which handles only one small aspect of that process or is it the whole show and handles everything?
The UIViewController would store an internal Property (UIImageView *)
which is in the Interface Builder connected with the UIImageView you
have created in the Xib file. So over these property you can change
through your Controller the image.
Does one viewController handle multiple images? is it like it's term, a "controller" for all the images presented on screen, or does it handle one image at a time?
Yes, this isn't a big problem. You can have as many images you want.
You just need to have the properties defined in the UIViewController
and linked to the View.
What is a viewControllers connection to the image(s) it handles? it contains references to them?
Yeah, its like a reference to the UIElement. You can then change
whatever property of the UIImageView you want directly from the
UIViewController
Some useful links:
Apple Official ViewController Guide
Apple Official ViewController Basics
You should have a look at Storyboards (U can use them since IOS 5.0)
I recommend you to check:
https://stackoverflow.com/questions/1939/how-to-articles-for-iphone-development-and-objective-c
Here are the answers to your questions:
No, it's doesn't handle graphics. It's the controller of the MVC design pattern. It handles the lifecycle of it's contents (for instance the views) and the data linked with.
A UIViewController is set as a root of an UIWindow. For instance, a UINavigationController is a subclass of UIViewController that stacks UIViewController in order to deal with the navigation.
Response in (1)
Try to be more specific with this question please.
As already commented, it's useful if you use the already built-in components like UINavigationController or UITabBarController.
For instance, you can have the data in instance variables and the display them in the contained UIView.
The UIView attached to your UIViewController will contain an UIImageView. Your UIViewController would have a connection with it in order to whatever changes you need, for instance, changing the image when the user press a button.
It can contain multiple UIViewsand therefore multiple UIImageViews (it's a subclass of UIView)
As commented, they would be contained on an UIImageView and would be linked programmatically or with an IBOutlet.
In a nutshell, a view controller is the controller in the MVC pattern. Please check this link before reading further so you're up to date with this pattern:
http://developer.apple.com/library/mac/#documentation/General/Conceptual/DevPedia-CocoaCore/MVC.html
OK, basically a controller manages a collection of views. It also fetches data from your model and sets the state of the views. It's important to note that the views know nothing of your model (your data), and the model knows nothing about your views. A controller also receives events from the views and decides how to change your model accordingly. It is essentially managing the synchronisation between your views and model.
There are technologies that help automate this such as KVO and key value binding. A google search will help you there.
One more thing. No other part of your application should access your views except for the controller. So generally in an application controllers tend to communicate with each other, for example via transitions or the delegate patterns between controllers under a navigation controller. So your application backbone tends to be controllers talking to each other.