[swift] How to check if a text field is empty or not in swift

if let ... where ... {

Swift 3:

if let _text = theTextField.text, _text.isEmpty {
    // _text is not empty here
}

Swift 2:

if let theText = theTextField.text where !theTextField.text!.isEmpty {
    // theText is not empty here
}

guard ... where ... else {

You can also use the keyword guard :

Swift 3:

guard let theText = theTextField.text where theText.isEmpty else {
    // theText is empty
    return // or throw
}

// you can use theText outside the guard scope !
print("user wrote \(theText)")

Swift 2:

guard let theText = theTextField.text where !theTextField.text!.isEmpty else {
    // the text is empty
    return
}

// you can use theText outside the guard scope !
print("user wrote \(theText)")

This is particularly great for validation chains, in forms for instance. You can write a guard let for each validation and return or throw an exception if there's a critical error.