#ibdesignable

in Xcode it is possible to change code at runtime and see the changes rendered live in the storyboard using IBDesignable. It is also possible to change user attributes live into the Interface Builder using IBInspectable. In this tutorial we will draw a square with a border. The width and color will be updated using this attributes. This tutorial is made with Xcode 10 and built for iOS 12.

Open Xcode and create a new Single View App.

For product name, use IOSLiveRenderingTutorial and then fill out the Organization Name and Organization Identifier with your customary values. Enter Swift as Language and choose Next.

Go to the File Menu and select File ->New -> File. Choose iOS->Source->Cocoa Touch Class and name the new class SquareView. Make it a subclass of UIView, and ensure the language is Swift. Click Next and then Create.

Go to the Storyboard and drag a View from the Object Library into the view controller's view. By default the View has a white background color, which makes this view invisible into the view controller's view. Select the view and go to the Attributes inspector. Change the background color to yellow. 

Select the yellow view and Go to the Size Inspector. Enter the following values.

The Storyboard now should look like this.

Next, set up the Auto Layout constraints.

Ctrl and drag from inside the yellow view and move the pointer slightly while staying inside the view. Hold the ctrl key and select "Width" and "Height".

Ctrl and drag from inside the yellow view and move the pointer down outside the yellow view. Hold the ctrl key and select "Leading Space to Container Margin" and "Top Space to Top Layout Guide".

Select the yellow View and go to the Identity inspector. In the Custom Class section change the class to SquareView.

Go to the SquareView.swift file and change the drawRect method

override func draw(_ rect: CGRect) { if let context = UIGraphicsGetCurrentContext() { // Set the outerline width context.setLineWidth(20.0) // Set the outerline colour UIColor.blue.set() // Create square context.addRect(rect) // Draw context.strokePath() } }

The outerline width of the square is set to 20 and the color is set to blue. This square is drawn over the yellow square from the storyboard. Build and Run the project to view the square.

Now imagine the outerline width needs to be changed to maybe 10 or 15, whatever looks best. It will be rather cumbersome to build and run the project each time to view the changes. It is possible to make a custom view render live using the @IBDesignable keyword. Add the following line before the SquareView class declaration.

@IBDesignable

Open the Assistant Editor and Manually Open the Storyboard view next to the already opened SquareView.swift file. Now change the outerline width to 10

CGContextSetLineWidth(context, 10.0)

The square's outerline width changes from 20 to 10 in the storyboard.

Properties marked with IBInspectable are editable in the Interface Builder's inspector panel. Add the following IBInspectable property in the SquareView class.

@IBInspectable var borderColor: UIColor = UIColor.blue { didSet { layer.borderColor = borderColor.cgColor } }

The property observer will update the borderColor of the underlying layer of the SquareView. Also, change the setting of the outerline blue color to

borderColor.set()

Now go to the storyboard and select the Square View. Go to the Attributes Inspector and the Border Color is now editable. Change the color to red, the outerlne color of the square changes to red in the storyboard.

original source : https://medium.com/@GeraldoBastos/whats-ibdesignable-ibinspectable-292829384e1

IBDesignable and IBInspectable are attributes used by Interface Builder, but different than IBOutlet and IBAction that are attributes too, IBInspectable and IBDesignable are used to render elements directly in Interface Builder.

These attributes showed in WWDC 14 [1] firstly supported to Objective-C, but now you can use with Swift too.

Rendering the custom UI component

The IBDesignable attribute is responsible to identifier the class inherits from the UIView that will render in Interface Builder.

For example, I created an ImageView custom using IBDesignable:

import UIKit

@IBDesignable class CustomImageView: UIImageView {

 override func prepareForInterfaceBuilder() {    self.layer.cornerRadius = self.bounds.size.width/2    self.layer.borderWidth = 6    self.layer.borderColor = UIColor.blackColor().CGColor    self.layer.masksToBounds = true  } }

You can see the result bellow:

But to get this result, I need to set in Identity Inspector the UIImageView to CustomImageView:

Configuring the UI component by Interface Builder

IBInspectable is another attribute that can be used to configure your UI component (e.g.), just you need to use this attribute in your code together with the property:

@IBInspectable var borderWidth: CGFloat = 6.0 {  didSet {    self.layer.borderWidth = self.borderWidth  } }

and the result is:

IBInspectable, unfortunately, can not use with all the types, see the list bellow that can support:

Int

CGFloat

Double

String

Bool

CGPoint

CGSize

CGRect

UIColor

UIImage

I would like that the next step for XCode is the possibility to create components, deliver and install it to the used inside of XCode the same form that native Apple’s components, but now, we need to use another road to share it (e.g.): GitHub [2], cocoapods [3], Carthage [4], etc…

References

[1] https://developer.apple.com/videos/play/wwdc2014/411/

[2] http://github.com

[3] https://cocoapods.org

original source : http://mhorga.org/2015/11/23/ibdesignable-and-ibinspectable.html

Last time we looked at two of the features of the Interface Builder: the Auto Layout and the Stack Views. Today we will look at one last trick, the @IBDesignable and @IBInspectable attributes. Let’s start by creating a new project in Xcode. We would like to have a custom view that consists of an image and some sort of subtitle for it. We are interested in seeing how they look at design time, before we even build and run the project. But stay with me here, you’re so close to finding out how to do that!

Let’s create a new class and name it CustomView.swift. Inside, let’s create a UIImageView and a UILabel and then add them to our view:

class CustomView : UIView {        var label: UILabel!    var imageView: UIImageView!        override init(frame: CGRect) {        super.init(frame: frame)        addSubviews()    }        required init?(coder aDecoder: NSCoder) {        super.init(coder: aDecoder)        addSubviews()    }        func addSubviews() {        imageView = UIImageView()        addSubview(imageView)        label = UILabel()        addSubview(label)    } }

Let’s also add the layoutSubviews() method to configure the image and label properties:

override func layoutSubviews() {    super.layoutSubviews()    layer.borderWidth = 0.5    layer.cornerRadius = 5    imageView.frame = self.bounds    imageView.contentMode = UIViewContentMode.ScaleAspectFit    label.frame = CGRectMake(0, bounds.size.height - 40, bounds.size.width, 40)    label.backgroundColor = UIColor.blackColor().colorWithAlphaComponent(0.1)    label.textAlignment = .Center    label.textColor = .grayColor() }

In the storyboard let’s add a UIView and in Identity Inspector change its class to CustomView, and finally set constraints for it, like this:

The imageview and label are displayed now, but they are both empty! Here comes the magic. Modify the class signature to include the @IBDesignableattribute and add the following method:

@IBDesignable class CustomView : UIView {        override func prepareForInterfaceBuilder() {        super.prepareForInterfaceBuilder()        label.text = " iPhone 6s Plus"        let url = "http://i.telegraph.co.uk/multimedia/archive/03058/iphone_6_3058505b.jpg"        imageView.image = UIImage(data: NSData(contentsOfURL: NSURL(string: url)!)!)    } ...

Now go to the storyboard and, voila! There is an image and text underneath. And all this was accomplished by using the IBDesignable attribute. There is a catch about the prepareForInterfaceBuilder() method though. Although it’s compiled for runtime, code called from prepareForInterfaceBuilder never gets called except by the Interface Builder at design time, so if you run the app nothing will displayed this time. Go ahead and see for yourself. So let’s comment out that method:

//    override func prepareForInterfaceBuilder() { //        super.prepareForInterfaceBuilder() //        label.text = " iPhone 6s Plus" //        let url = "http://i.telegraph.co.uk/multimedia/archive/03058/iphone_6_3058505b.jpg" //        imageView.image = UIImage(data: NSData(contentsOfURL: NSURL(string: url)!)!) //    }

Next, let’s make use of the other attribute we mentioned in the beginning, @IBInspectable. So let’s add this last piece of code we need:

@IBInspectable var text: String? {    didSet { label.text = text } } @IBInspectable var image: UIImage? {    didSet { imageView.image = image } }

This allows us to set values for variables in Attributes Inspector so if you go there now, you will notice a new section appears for our UIView, named CustomView, under Attributes Inspector, and it has two fields: Text and Image. If you want, you could download that iPhone image from the URL we used above (or any other image you want) and add it to the project. Next, if you click the Image drop down menu, you should be able to choose it, and it will be displayed in real time, like this:

Lastly, write iPhone 6s Plus (or anything else you want) and it will show on the label on top of the image, in real time as well:

These are two powerful attributes that are very useful when designing your apps, without having to actually build and run your app. There are unlimited opportunities for using these attributes. Imagine playing with numbers that show a completion wheel spinning in real time, or colors that change as you are watching them live.

Funny story - inherited UIButton, made the class @IBDesignable, created an @IBInspectable property, set some value in InterfaceBuilder. Then decided the property name was stupid and renamed it and bam! My app crashed with a bizarre error:

Failed to set (propertyName) user defined inspected property on (assessment.DCDropdownButton): [<assessment.DCDropdownButton 0x13fd2ea00> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key propertyName.

So yes, you guessed it - I had to go back and rename the property to its original name and remove its default value from IB before I re-rename it. And the error was gone.