@IBDesignable error: IB Designables: Failed to update auto layout status: Interface Builder Cocoa Touch Tool crashed

Question

I have a very simple subclass of UITextView that adds the "Placeholder" functionality that you can find native to the Text Field object. Here is my code for the subclass:

import UIKit
import Foundation

@IBDesignable class PlaceholderTextView: UITextView, UITextViewDelegate
{
    @IBInspectable var placeholder: String = "" {
        didSet {
            setPlaceholderText()
        }
    }
    private let placeholderColor: UIColor = UIColor.lightGrayColor()        
    private var textColorCache: UIColor!
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.delegate = self
    }
    
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.delegate = self
    }
    
    func textViewDidBeginEditing(textView: UITextView) {
        if textView.text == placeholder {
            textView.text = ""
            textView.textColor = textColorCache
        }
    }
    
    func textViewDidEndEditing(textView: UITextView) {
        if textView.text == "" && placeholder != "" {
            setPlaceholderText()
        }
    }
    
    func setPlaceholderText() {
        if placeholder != "" {
            if textColorCache == nil { textColorCache = self.textColor }
            self.textColor = placeholderColor
            self.text = placeholder
        }
    }
}

After changing the class for the UITextView object in the Identity Inspector to PlaceholderTextView, I can set the Placeholder property just fine in the Attribute Inspector. The code works great when running the app, but does not display the placeholder text in the interface builder. I also get the following non-blocking errors (I assume this is why it's not rendering at design time):

error: IB Designables: Failed to update auto layout status: Interface Builder Cocoa Touch Tool crashed

error: IB Designables: Failed to render instance of PlaceholderTextView: Rendering the view took longer than 200 ms. Your drawing code may suffer from slow performance.

I'm not able to figure out what is causing these errors. The second error doesn't make any sense, as I'm not even overriding drawRect(). Any ideas?

Answer 1

There are crash reports generated when Interface Builder Cocoa Touch Tool crashes. Theses are located in ~/Library/Logs/DiagnosticReports and named IBDesignablesAgentCocoaTouch_*.crash. In my case they contained a useful stack-trace that identified the issue in my code.