UI Test deleting text in text field

I wrote an extension method to do this for me and it's pretty fast:

extension XCUIElement {
    /**
     Removes any current text in the field before typing in the new value
     - Parameter text: the text to enter into the field
     */
    func clearAndEnterText(text: String) {
        guard let stringValue = self.value as? String else {
            XCTFail("Tried to clear and enter text into a non string value")
            return
        }

        self.tap()

        let deleteString = String(repeating: XCUIKeyboardKey.delete.rawValue, count: stringValue.count)

        self.typeText(deleteString)
        self.typeText(text)
    }
}

This is then used pretty easily: app.textFields["Email"].clearAndEnterText("[email protected]")

this will work for textfield and textview

for SWIFT 3

extension XCUIElement {
    func clearText() {
        guard let stringValue = self.value as? String else {
            return
        }

        var deleteString = String()
        for _ in stringValue {
            deleteString += XCUIKeyboardKeyDelete
        }
        self.typeText(deleteString)
    }
}

for SWIFT 4, SWIFT 5

extension XCUIElement {
    func clearText() {
        guard let stringValue = self.value as? String else {
            return
        }

        var deleteString = String()
        for _ in stringValue {
            deleteString += XCUIKeyboardKey.delete.rawValue
        }
        typeText(deleteString)
    }
}

UPDATE XCODE 9

There is an apple bug where if the textfield is empty, value and placeholderValue are equal

extension XCUIElement {
    func clearText() {
        guard let stringValue = self.value as? String else {
            return
        }
        // workaround for apple bug
        if let placeholderString = self.placeholderValue, placeholderString == stringValue {
            return
        }

        var deleteString = String()
        for _ in stringValue {
            deleteString += XCUIKeyboardKey.delete.rawValue
        }
        typeText(deleteString)
    }
}