Swifting Around

tl;dr

I’m going to make a simple tableview with a custom cell type, use the new UIVisualEffectView from iOS 8 and then show off a bit of the power of Swift. It should take you about ~30 minutes to go through all the steps. Enjoy!

full code

if you are looking for a simpler tutorial for tableviews check out this one

Create a new project

Open Xcode 6, create a new “Single Page Application” and select Swift as the programming language.

create a single page application in Xcode

Add a table view property

Open the ViewController.swift class and add a new tableview instance variable below the class declaration. Add the @IBOutletInterface Builder declaration attribute to expose the tableView property.

“Interface Builder attributes are declaration attributes used by Interface Builder to synchronize with Xcode. Swift provides the following Interface Builder attributes: IBAction, IBDesignable, IBInspectable, and IBOutlet. These attributes are conceptually the same as their Objective-C counterparts.”

Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks. https://itun.es/ro/jEUH0.l

class ViewController: UIViewController {

    @IBOutlet var tableView: UITableView!

    ...

}

Conform to the UITableViewDelegate and UITableViewDataSource protocols

To conform to the UITableViewDelegate and UITableViewDataSource protocol, just add them separated by commas afterUIViewController in the class declaration. (more about protocols in Apple’s Docs)

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

}

Add a table view in your view controller interface

Open Main.storyboard and drag a UITableView from the library (in the lower right corner) into the ViewController view.

add a table in interface builder

Connect the Interface Builder outlets

Connect the dataSourcedelegate and tableView outlets in interface builder. Just right click on the table view and then connect them.

connect interface builder outlets

Create the custom cell class

Create a new class above your ViewController code. Your custom cell class should inherit from UITableViewCell! Add outlets for the backgroundImage and titleLabel.

class CustomTableViewCell : UITableViewCell {
    @IBOutlet var backgroundImage: UIImageView
    @IBOutlet var titleLabel: UILabel
}

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

}

Create the custom cell interface

Right click on your applications directory and select new file.

add a new file in xcode

Select User Interface and then the Empty template. Select iPhone and name it CustomTableViewCell.

Open CustomTableViewCell.xib and add a UITableViewCell in it from the component library. Select the Table View Cell and change it’s class to CustomTableViewCell

change a class in interface builder

After that the table view cell should change its name to Custom Table View Cell, the backgroundImage and titleLabel outlets should be visible now.

Add an image view and a label in the cell.

Resize the cell to 320 x 320 using the size inspector. And set the row height to 320

resising the cell and setting the row height

Connect the cell outlets to the CustomTableCellViewCell. Notice that custom view bind outlets to the view object and custom view controllers bind them to the File's Owner

connect the custom cell outlets

Add the loadItem method

In a real life application you usualy have more than one type of cell in a table view (or collection view). By keeping the initialization logic in the cell we can avoid code duplication or spaghetti code.

This cell displays an image stored on the device and has a string title. All we need to do during the cell initialization is to set the image and the tile.

class CustomTableViewCell : UITableViewCell {
    @IBOutlet var backgroundImage: UIImageView!
    @IBOutlet var titleLabel: UILabel!

    func loadItem(#title: String, image: String) {
        backgroundImage.image = UIImage(named: image)
        titleLabel.text = title
    }
}

Obs: For you Objective-C folks in Swift you do not need to call properties using the self keyword! Use the self keyword only when you have a parameter named like your property, so that the compiler can understand your code.

Note: This function uses a shorthand external parameter name. If the method declaration was func loadItem(title: String, image: String) (without # symbol) to call it we would have to write cell.loadItem("We❤Swift", image: "someimage.jpeg"). Instead, with the # symbol, to call loadItem we would write cell.loadItem(title: "We❤Swift", image: "someimage.jpeg"). I think the second method is clearer.

From Apple’s Docs:

Shorthand External Parameter Names

If you want to provide an external parameter name for a function parameter, and the local parameter name is already an appropriate name to use, you do not need to write the same name twice for that parameter. Instead, write the name once, and prefix the name with a hash symbol (#). This tells Swift to use that name as both the local parameter name and the external parameter name.

Add some data to display

Download the swifts and add them in your project. Unarchive the zip file and drag the files in you Xcode Navigator. Make sure to check Copy items if needed.

For each custom cell we need a title and a image name, we are going to store them in an Array of Tuples.

From Apple’s Docs:

A tuple pattern is a comma-separated list of zero or more patterns, enclosed in parentheses. Tuple patterns match values of corresponding tuple types.

A pattern represents the structure of a single value or a composite value. For example, the structure of a tuple (1, 2) is a comma-separated list of two elements. Because patterns represent the structure of a value rather than any one particular value, you can match them with a variety of values. For instance, the pattern (x, y) matches the tuple (1, 2) and any other two-element tuple. In addition matching a pattern with a value, you can extract part or all of a composite value and bind each part to a constant or variable name.

In Swift, patterns occur in variable and constant declarations (on their left-hand side), in for-in statements, and in switch statements (in their case labels). Although any pattern can occur in the case labels of a switch statement, in the other contexts, only wildcard patterns, identifier patterns, and patterns containing those two patterns can occur. …

The first value will represent the title and the second one the imageName.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    var items: [(String, String)] = [
        ("❤", "swift 1.jpeg"),
        ("We", "swift 2.jpeg"),
        ("❤", "swift 3.jpeg"),
        ("Swift", "swift 4.jpeg"),
        ("❤", "swift 5.jpeg")
    ]

}

Set the number of rows

Implement tableView(_:numberOfRowsInSection:) and return the number of items.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count;
    }

}

Note: In iOS the number of sections is 1 by default, so we do not need to set a value for that. In case you want to create a table with multiple sections just implement the numberOfSectionsInTableView(_:) method.

Register the Nib

Load the CustomTableViewCell interface file into a UINib object and then tell the table view to use it for the customCell reuse identifier.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    override func viewDidLoad() {
        ...

        var nib = UINib(nibName: "CustomTableViewCell", bundle: nil)

        tableView.registerNib(nib, forCellReuseIdentifier: "customCell")
    }

    ...

}

Create the cell

Now when you will ask for a cell from the table view with the reuse identifier customCell, the tableView will look for any unused cells with that reuse identifier or just create one using the CustomTableViewCell nib.

The tableView will call the tableView(_:cellForRowAtIndexPath:) method on the dataSource whenever it need a specific cell. The location of the cell is stored in an NSIndexPath that has a row and section property.

To create a cell all we need to do is ask for one using the dequeueReusableCellWithIdentifier(_:) method. After we have a cell we need to load the title and image and then return it.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        var cell:CustomTableViewCell = self.tableView.dequeueReusableCellWithIdentifier("customCell") as CustomTableViewCell

        // this is how you extract values from a tuple
        var (title, image) = items[indexPath.row]

        cell.loadItem(title: title, image: image)

        return cell
    }

}

Handle Table Selection

When a cell is selected the table view will call the tableView(_:didSelectRowAtIndexPath:) method on the delegate. To handle table view selection all you need to do is implement that method.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        tableView.deselectRowAtIndexPath(indexPath, animated: true)
        println("You selected cell #\(indexPath.row)!")
    }
}

If you run the project it should look like this:

table view with custom cells in swift

Add a blur view

In iOS 8 we now have a easy way of recreating the blur effect used throughout the system. UIVisualEffectView is a subclass ofUIView that provides a simple abstraction over complex visual effects. UIKit has two implemented effects UIBlurEffect andUIVibrancyEffect.

Let’s create a UIVisualEffectView and add it to the main view.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    override func viewDidLoad() {
        ...

        addEffect()

        ...
    }

    func addEffect() {
        var effect = UIBlurEffect(style: UIBlurEffectStyle.Light)

        var effectView = UIVisualEffectView(effect: effect)

        effectView.frame = CGRectMake(0, 0, 320, 100)

        view.addSubview(effectView)
    }

    ...
}

table view with UIBlurEffect in iOS 8 using swift

There are 3 type of blur effects. If we send the effect and offset as a parameters to the addEffect method we can reuse the code and see all three blur effects at once.

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    ...

    override func viewDidLoad() {
        super.viewDidLoad()

        addEffect(UIBlurEffect(style: UIBlurEffectStyle.Light), offset: 0)
        addEffect(UIBlurEffect(style: UIBlurEffectStyle.Dark), offset: 50)
        addEffect(UIBlurEffect(style: UIBlurEffectStyle.ExtraLight), offset: 100)

        var nib = UINib(nibName: "CustomTableViewCell", bundle: nil)

        tableView.registerNib(nib, forCellReuseIdentifier: "customCell")
    }

    func addEffect(effect: UIVisualEffect, offset: CGFloat) {
        var effectView = UIVisualEffectView(effect: effect)

        effectView.frame = CGRectMake(0, offset, 320, 50)

        view.addSubview(effectView)
    }

    ...

}

the 3 types of blur

Extend the Array class

In ruby the Array class two nifty methods each and eachWithIndex. The each method takes a function as a parameter and calls it with each element of the array in order, eachWithIndex takes a function as a parameter and calls it with the tuple (element, index)for each element.

We can extend a class using the extension keyword. The implementation of each and eachWithIndex in Swift would look like this:

extension Array {
    func each(callback: T -> ()) {
        for item in self {
            callback(item)
        }
    }

    func eachWithIndex(callback: (T, Int) -> ()) {
        var index = 0
        for item in self {
            callback(item, index)
            index += 1
        }
    }
}

Putting it all together

Now we have 3 method calls that look pretty similar. Two things change: the style and offset.

    override func viewDidLoad() {
        ...

        addEffect(UIBlurEffect(style: UIBlurEffectStyle.Light), offset: 0)
        addEffect(UIBlurEffect(style: UIBlurEffectStyle.Dark), offset: 50)
        addEffect(UIBlurEffect(style: UIBlurEffectStyle.ExtraLight), offset: 100)

        ...
    }

We can rewrite this code using eachWithIndex:

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
    ...

    override func viewDidLoad() {
        ...

        addEffects()

        ...
    }

    func addEffects() {
        [
            UIBlurEffect(style: UIBlurEffectStyle.Light),
            UIBlurEffect(style: UIBlurEffectStyle.Dark),
            UIBlurEffect(style: UIBlurEffectStyle.ExtraLight)
        ].eachWithIndex { (effect, index) in
            var effectView = UIVisualEffectView(effect: effect)

            effectView.frame = CGRectMake(0, CGFloat(50 * index), 320, 50)

            self.view.addSubview(effectView)
        }
    }

    ...
}

We can do one thing here and use the map function:

func addEffects() {
    [
        UIBlurEffectStyle.Light,
        UIBlurEffectStyle.Dark,
        UIBlurEffectStyle.ExtraLight
    ].map {
        UIBlurEffect(style: $0)
    }.eachWithIndex { (effect, index) in
        var effectView = UIVisualEffectView(effect: effect)

        effectView.frame = CGRectMake(0, CGFloat(50 * index), 320, 50)

        self.view.addSubview(effectView)
    }
}

This is called method chaining. You can read more about closures and higher order functions in Silviu’s post here.

the final result

You can get the code here.

Challenges:

  • use more than one type of cell in the same table view
  • implement more of the dataSource and delegate methods and see what you can do with them. You could start withnumberOfSectionsInTableView(_:)tableView(_:titleForHeaderInSection:)sectionIndexTitlesForTableView(_:),tableView(_:heightForRowAtIndexPath:)
  • make a Contact Book App (hint: finish the second challenge first)

I’ve been using similar patterns in Objective-C but they were always a pain because of the syntax and limitations of blocks. I Hope you got a bit excited about functional programming and Swift.

If you found this useful, please take a moment and share it with your friends :)

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  45 comments for “Swifting Around

  1. oliver
    June 6, 2014 at 3:36 am

    great guide! thanks a lot!

  2. June 8, 2014 at 5:32 pm

    Are you sure that your explanation of “shorthand external parameter name” is correct?

    • June 8, 2014 at 5:38 pm

      It’s incomplete. You could also use

      func doubleAnInt(shortName verboseNameThatWillBeUsedInsideTheFunction: Int) {
      return verboseNameThatWillBeUsedInsideTheFunction * 2
      }

      doubleAnInt(shortName: 2) // 4

  3. Chris
    June 8, 2014 at 10:04 pm

    Hi, thanks for an awesome quick tutorial. I’m having trouble applying the blur effect, the result I’m getting is not similar to your. My blur view is not very transparent (so you almost can’t see the content behind). This is replicated in playground using this code:

    `let imageView = UIImageView(image: UIImage(named: “/Users/Buusmann/bg.jpg”))
    imageView.frame = CGRectMake(0, 0, 1024, 768)

    var effectView = UIVisualEffectView(effect: UIBlurEffect(style: .Light))

    effectView.frame = CGRectMake(0, 0, 1024, 768)
    imageView.addSubview(effectView)
    `

    Have you got any suggestions as to why this would be?

    Thanks in advance
    Chris

    • June 8, 2014 at 10:16 pm

      I managed to replicate the behaviour you described. Just add the visual effect view in the view that contains imageView and it should work.

      * view
      |
      *- Image View
      *- Visual Effect

      • Chris
        June 9, 2014 at 6:35 am

        I tried this, and still no luck unfortunately. Can it have something to do with an alpha value?

  4. Irina
    June 9, 2014 at 5:11 pm

    Hello. good tutorial!

    I am having a problem though. After attaching everything I am getting “fatal error: Can’t unwrap Optional.None” in my loadItem because the compiler thinks my background and label doesn’t exist. But they are hooked up in the nib file! Please help.

    backgroundImage.image = UIImage(named: image)
    titleLabel.text = title

  5. Johne691
    June 10, 2014 at 2:04 am

    Very efficiently written post. It will be valuable to anyone who usess it, as well as myself. Keep doing what you are doing i will definitely read more posts.

  6. DeFrenZ
    June 10, 2014 at 9:51 am

    about that eachwithindex method… look into the enumerate function ;)

  7. June 14, 2014 at 4:34 am

    I love it when individuals come together and share opinions.
    Great website, keep it up!

  8. rikin
    June 17, 2014 at 11:49 pm

    when i run the project (done until registering the nib and handling selection) it throws an error at line
    tableView.registerNib(nib, forCellReuseIdentifier: “customCell”)
    says : EXC_BAD_INSTRUCTION.
    any idea why ?

    • June 18, 2014 at 1:42 pm

      does tableView or nib have an optional type?

  9. rikin
    June 17, 2014 at 11:50 pm

    and in the console it says
    can’t unwrap optional.none

    any help is appreciated.

  10. June 23, 2014 at 3:57 pm

    Thanks for your great article!

    I found other blogs use registerClass to load custom table view. Something like this:
    self.tableView.registerClass(CustomTableViewCell.self, forCellReuseIdentifier: “customCell”)

    Would it be an alternative way to load custom Table View Class? What is the use case for this method?

    • June 23, 2014 at 4:33 pm

      the registerNib/registerClass method tells the tableView how to create a cell for a cell reuse identifier. You can use any method that solves your problem

  11. Fred
    July 1, 2014 at 2:30 am

    Hi Andrei, great tutorial. When I’m running the project I’m getting a giant grey rectangle that is overlaying the image. I can only see the left most edge of the image so I can tell its there. I’ve downloaded your source code and compared all of the properties and everything seems to be the same. Any idea what it can be? (btw using beta 2 – don’t know if that makes a difference but thought I would throw it out there)

    • Trevor
      July 17, 2014 at 6:36 am

      I’m getting the same thing. Using beta 3. With the 3d exploded view, i can see all images are there stacked on top of one another with several small UITableViewCellSeparatorView instances on the very top of the stack of images.

      • Trevor
        July 17, 2014 at 7:07 am

        Figured it out! Add function:

        func tableView(tableView:UITableView!, heightForRowAtIndexPath indexPath:NSIndexPath)->CGFloat
        {

        return 320
        }

        • Jamie
          December 25, 2014 at 3:06 am

          This also corrected my issue. Any chance we can have this added into the main article with an explanation?

  12. Joe
    July 1, 2014 at 5:30 pm

    Hi

    This is a nice tutorial but this blur effect why dont work with only text? I see the text dissapear or dont add the blur effect

    • Kirke
      July 20, 2014 at 8:04 pm

      My understanding (based on watching WWDC videos) is that the blur effect that Apple designed intentionally handles text differently (ignores it) to prevent distraction.

  13. Will
    July 19, 2014 at 12:46 am

    I added another line of code for the purpose of my app, and getting a “property ‘self.nameLabel’ not initialized at super.init call” error message, however I followed the steps exactly how you have showed. I checked twice for any possible error that could’ve happened on my part. Is it just the swift beta 3 acting buggy?

  14. Will
    July 19, 2014 at 12:51 am

    nevermind!! Figured it out.

  15. September 3, 2014 at 3:38 pm

    This worked! Couldn’t get custom cells to work any other way. Long live the xib! :)

  16. Andrew
    October 23, 2014 at 3:34 am

    I think I must’ve connected some of the Table View outlets wrong — I’m pretty new to Xcode, and that part wasn’t very specific — but on the line declaring the ViewController class, I get an error: “ViewController does not conform to protocol “UITableViewDataSource”

    Anybody know what I’m doing wrong?

    • October 23, 2014 at 2:08 pm

      The tableView parameter is now an implicitly unwrapped optional now. UITableView -> UITableView!

      • Andrew
        October 24, 2014 at 8:24 pm

        Now I’m having a problem where cells don’t want to change size to match their contents — each table row is the default system size, and the images just seem to overlap them (and also appear to be simply displaying as each images’ actual size, instead of filling the cell area).

        Constraint issue, maybe? Not sure how to fix this.

  17. Frederick C. Lee
    November 4, 2014 at 7:14 pm

    Current Environment: Xcode 6.1, iOS 8.1
    Your code is now obsolete. It doesn’t compile …violates protocol, etc.

    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:12:5: ‘IBOutlet’ property has non-optional type ‘UIImageView’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:13:5: ‘IBOutlet’ property has non-optional type ‘UILabel’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:39:5: ‘IBOutlet’ property has non-optional type ‘UITableView’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:11:7: Class ‘CustomTableViewCell’ has no initializers
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:12:1: ‘required’ initializer ‘init(coder:)’ must be provided by subclass of ‘UITableViewCell’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:37:7: Class ‘ViewController’ has no initializers
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:38:1: ‘required’ initializer ‘init(coder:)’ must be provided by subclass of ‘UIViewController’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:37:1: Type ‘ViewController’ does not conform to protocol ‘UITableViewDataSource’
    /tmp/UIVisualEffectView/UIVisualEffectView/ViewController.swift:59:31: Value of optional type ‘UINib?’ not unwrapped; did you mean to use ‘!’ or ‘?’?

    • November 4, 2014 at 7:30 pm

      I updated the code and the article. It should work now. There where some changes in the delegate method declarations.

  18. Christopher Dyer
    November 13, 2014 at 1:02 pm

    Bravo Andrei, a really nicely structured tutorial with good explanations and extension of concepts. It must be a nightmare to offer this sort of thing right now, as Swift keeps changing. Good on you for sharing.

  19. Rohan
    November 30, 2014 at 10:22 am

    Great Tutorial, with a bit of persistence I was able to figure out your tutorial (First time coding iOS apps ever). Just a question: how come the height of the tableView row height is 320 and the custom cell height is also 320 is there anyway to make it flexible aka say for different image heights

    • November 30, 2014 at 12:45 pm

      use the tableView:heightForRowAtIndexPath: method for that

  20. December 2, 2014 at 10:41 am

    Thank you for great explanation. You tutorial saved a lot of hours for me.

  21. December 5, 2014 at 12:25 pm

    Thanks Andrei great article, I am new to Swift and I am having some problems trying to access the elements inside the custom cell, this is my code for didDeselectRowAtIndexPath.

    I want to pass the value of the current cell to another controller but xCode keeps complaining about it can’t find the label inside my custom cell.

    Do I have to make IBOutlets publics inside our custom cell class in some way?

    func tableView(tableView: UITableView, didDeselectRowAtIndexPath indexPath: NSIndexPath) {
    categoriesTableView.deselectRowAtIndexPath(indexPath, animated: true)
    println(indexPath.row)
    let currentCell = categoriesTableView.cellForRowAtIndexPath(indexPath)! as UITableViewCell
    let currentCategory = currentCell.categoryLabel.text <— got error here!
    performSegueWithIdentifier("toSubCategories", sender: self)

    //navigationController?.pushViewController(ProductListViewController(), animated: true)
    }

    Thanks for some tips!

    • December 5, 2014 at 2:40 pm

      Try let currentCategory = currentCell.categoryLabel?.text

      • December 5, 2014 at 6:51 pm

        Thanks but it didn’t work for me, at the end I solve it reading the model using the indexPath and passing the data to the second controller.

  22. L'Lay
    January 25, 2015 at 1:53 pm

    Great Tutorial!
    This is exactly what i was looking for, to fully custom my Cell construction.
    Great website as well, keep it this way Andrei.
    THX

  23. Angela
    January 27, 2015 at 6:44 pm

    Following this tutorial to get custom tableview cell, getting following error on line –
    var nib = UINib(nibName: “CustomTableViewCell”, bundle: nil)

    tableView.registerNib(nib, forCellReuseIdentifier: “customCell”)<——-

    fatal error: unexpectedly found nil while unwrapping an Optional value

  24. Anatole
    March 29, 2015 at 11:13 am

    Hey and thank you very much for the tuto!

    I’m getting an issue while trying to register the nib.
    Xcode keeps telling me ‘(UITableView, numberOfRowsInSection: Int) -> Int’ does not have a member named ‘registerNib’

    I searched a lot on google but nobody seems to have this issue…
    Thank’s again.

    Best,

    Anatole

    Code:

    override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    var nib = UINib(nibName: “CommentTableViewCell”, bundle: nil)

    tableView.registerNib(nib, forCellReuseIdentifier: “commentCell”)

    }

    • Anatole
      March 29, 2015 at 1:44 pm

      Hey again and thank’s for reading me!

      I resolved this issue but now I have many problems:

      EXC_BAD_INSTRUCTION one the registerNib line when launching the application
      self.tableView.registerNib(nib, forCellReuseIdentifier: “commentCell”)

      If on that line I use tableView? instead of tableView, then it’s ok but

      SIG ABORT on the dequeue line when launching the application
      var cell:CommentTableViewCell = self.tableView?.dequeueReusableCellWithIdentifier(“commentCell”, forIndexPath: indexPath) as CommentTableViewCell

      Thank’s again.

      Best,

      Anatole

      • March 30, 2015 at 10:25 am

        Did you connect the tableView IBOutlet ?

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