iOS Tip: Using IBDesignable for previewing custom views

Xcode 6 offers you an amazing feature that help developers save A LOT of time by allowing you to preview the output even without having to run the application for your custom drawn views.

IBDesignable as it is called, when applied on your custom view allows you to preview it directly on the storyboard before you having to run the code after any change.


Just prefix your custom view with IBDesignable Yes. and that’s all you need to do!! 🙂


You can try this out using the iOS single view application template in Xcode.

Here’s the code within the custom UIView subclass in the file simpleView.swift.


class simpleView: UIView {
    // Override Draw Rect method to perform custom drawing.
    override func drawRect(rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()

        // ************************************************************
        // Paint the View Blue
        CGContextSetFillColorWithColor(context, UIColor.blueColor().CGColor)  // Set fill color
        CGContextFillRect(context, rect) // Fill rectangle using the context data

        // ************************************************************
        // Paint a rect inside view Green
        let greenRect = CGRectInset(rect, 30, 30) // Inset will reduce the size of 'rect' by 30 in x and 30 in y.
        CGContextSetFillColorWithColor(context, UIColor.greenColor().CGColor) // Set fill color
        /* Fill `rect' with the current fill color. */
        CGContextFillRect(context, greenRect) // Fill rectangle using the context data

Now you can add this view as a subview to any view in your storyboard. The changes you do in the view will immediately reflect in the storyboard (actually it still needs to build so it might take a little while ;)).


Debugging with IBDesignable

Better yet, you can debug the code within your custom view class using IBDesignable without running the app. All you need to do is add/enable breakpoints in your custom view code and then select the corresponding view in storyboard and click on Xcode: Editor -> Debug Selected Views and voila! There it is.


And.. You’re welcome! 😉

Further Reads:

  1. Apple Developer: Creating a Custom View That Renders in Interface Builder
  2. Apple Developer: Debugging a Custom View Without Running Your App
  3. NSHipster: IBInspectable / IBDesignable

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