Swift bad execution when checking length - swift

Question

I am trying to evaluate the contents of a form field that, when empty is throwing an error.
Here is the outlet code
#IBOutlet var txtUsername : UITextField!
Here is the println for the target field.
println("\(txtUsername)")
<UITextField: 0x10e8280a0; frame = (20 40; 280 30); text = ''; clipsToBounds = YES; opaque = NO; autoresize = RM+BM; gestureRecognizers = <NSArray: 0x10e828b20>; layer = <CALayer: 0x10e828300>>
So, looking at this I would assume that txtUsername.text is empty or == "". But everything I try to do to evaluate this throws an error.
if countElements(txtUsername.text as String) != 0 {
... code here
}
if txtUsername.text.bridgeToObjectiveC().length != 0 {
... code here
}
if txtUsername.text.utf16count != 0 {
... code here
}
if txtUsername.text != "" {
... code here
}
All bring back "EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
Also, evaluating whether it is nil doesn't seem to work. The below scripts show that there is something to be evaluated, even though it is blank. The problem is telling whether or not it is blank.
If the field was nil, I would expect it to return false and trigger the else statement.
if let evalText = txtUsername.text{
println("There is something here : \(evalText)")
} else {
println("text is nil")
}
// This returns "There is something here:"
if txtUsername.text{
println("There is something here")
} else {
println("text is nil")
}
// This returns "There is something here"
I have even tried to set the value in a variable, only to have it kick out the error after hitting the "if" statement.
Thanks,

Answer 1

EXC_BAD_INSTRUCTION implies an assertion failure. This is most common when something is nil but you are still trying to operate on it.
The text property of UITextField is an Implicitly Unwrapped Optional (String!). You must first check if it is nil. Your app is crashing because it is nil.

Answer 2

txtUsername.text is an optional in Swift. Even your label is an optional so it's not really safe to use ! when declaring it. But anyway, try using this:
if let currentText = txtUsername.text {
// ... Do something with currentText ...
}
else {
NSLog("Text is nil")
}
To be extra sure you can even check if txtUsername is set in the same way. So in the end you will have this:
if let currentTxtUsername = txtUsername{
if let currentText = currentTxtUsername.text {
// ... Do something with currentText ...
}
else {
NSLog("Text is nil")
}
}
else {
NSLog("Text label is nil")
}
Don't forget to remove the ! in the declaration part though.

Answer 3

Turned out to be an error ghosting issue.
The actual problem was that it would get further down in the code and run into a situation where I was inadvertently trying to put nil data from a core data object back into the text string. Setting a text field to nil doesn't work, but rather than error where the problem was, it erred at the "if" statement 20 lines above it.
Below is the full code, and some description of the issue.
#IBAction func btnLoad(sender : AnyObject) {
var appDel = (UIApplication.sharedApplication().delegate as AppDelegate)
var context = appDel.managedObjectContext
var request = NSFetchRequest(entityName: "Users")
request.returnsObjectsAsFaults = false
// Here is the place where it throws the error.
if txtUsername.text == "" {
request.predicate = NSPredicate(format: "username = %#", "\(txtUsername.text)")
}
var results = context.executeFetchRequest(request, error: nil)
println(results)
if(results.count > 0){
var res = results[0] as NSManagedObject
println("\(res)")
//*** The database had nil values for the result selected. And nil doesn't go into a text field.
txtUsername.text = res.valueForKey("username") as String
txtPassword.text = res.valueForKey("password") as String
responseLabel("User Found")
} else {
responseLabel("No Users Found")
}
}
Thanks everyone for replying.