Why does shouldChangeTextInRange get called multiple times using predictive input? - objective-c

Question

The predictive-input of iOS8 calls the following delegate method of UITextView multiple times resulting in the selected word being inserted multiple times into the view.
This code works for typing single letters and copy/paste but not when using the predictive-input bar; why not?
- (BOOL) textView:(UITextView*)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text
{
textView.text = [textView.text stringByReplacingCharactersInRange:range withString:text];
return false;
}
With this code; if I enter an empty UITextView and tap on "The" in the predictive text (autocomplete) view it inserts "The The" into the view by way of making three calls on this method. The parameters passed in for each call are:
range : {0,0} text : #"The"
range : {0,0} text : #"The"
range : {3,0} text : #" "
The space I can understand; but why insert "The" twice?

Answer 1

I got this same issue. It appears that with predictive text, setting textView.text in that delegate method triggers an immediate call to that delegate method again (this only happens with predictive text as far as I know).
I fixed it by just surrounding my textView changes with a guard:
private var hack_shouldIgnorePredictiveInput = false
func textView(textView: UITextView!, shouldChangeTextInRange range: NSRange, replacementText text: String!) -> Bool {
if hack_shouldIgnorePredictiveInput {
hack_shouldIgnorePredictiveInput = false
return false
}
hack_shouldIgnorePredictiveInput = true
textView.text = "" // Modify text however you need. This will cause shouldChangeTextInRange to be called again, but it will be ignored thanks to hack_shouldIgnorePredictiveInput
hack_shouldIgnorePredictiveInput = false
return false
}

Answer 2

I modified the accepted answer from Richard Venable, because, as JLust noted in the comment, that 3rd call with the space was throwing me off.
I added
private var predictiveTextWatcher = 0
And
if predictiveTextWatcher == 1 {
predictiveTextWatcher = 0
return false
}
if hack_shouldIgnorePredictiveInput {
predictiveTextWatcher += 1
hack_shouldIgnorePredictiveInput = false
return false
}
It's all pretty hacky, but better than nothing.
Best,

Answer 3

Not an answer, but a safer workaround:
class TextViewTextChangeChecker {
private var timestamp: TimeInterval = 0
private var lastRange: NSRange = NSRange(location: -1, length: 0)
private var lastText: String = ""
func shouldChange(text:String,in range: NSRange) -> Bool {
let SOME_SHORT_TIME = 0.1
let newStamp = Date().timeIntervalSince1970
let same = lastText == text && range == lastRange && newStamp - timestamp < SOME_SHORT_TIME
timestamp = newStamp
lastRange = range
lastText = text
return !same
}
}
still this didn't helped me because changing the textView from the shouldChangeTextInRange function changed the autocapitalizationType to .word (only by behaviour, not the field itself).