how to properly error handle XCUI element not found in swift - ios

Question

I am trying to write a do-try-catch in swift for my iOS UI test which uses XCUI testing. I am reading the error-handling section: https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html#//apple_ref/doc/uid/TP40014097-CH42-ID508
but am unsure of which error should be thrown when an element is not found.
func tapElement(string:String) throws {
do{
waitFor(app.staticTexts[string], 5)
try app.staticTexts[string].tap()
}
catch {
NSLog("Element was not found: \(string)")
//how can i check specifically that the element was not found?
}
}
....
func waitFor(element:XCUIElement, seconds waitSeconds:Double) {
NSLog("Waiting for element: \(element)")
let exists = NSPredicate(format: "exists == 1")
expectationForPredicate(exists, evaluatedWithObject: element, handler: nil)
waitForExpectationsWithTimeout(waitSeconds, handler: nil)
}
any help greatly appreciated!!

Answer 1

You should use element.exists AND element.isHittable
element.exists checks whether the element is an element of the UIApplication/ScrollView/..
element.isHittable determines if a hit point can be computed for the element.
If you don't check for both, than element.tap() throws the following error, for example, if the element is under the keyboard:
Failed: Failed to scroll to visible (by AX action) TextField,...
Example code:
let textField = elementsQuery.textFields.allElementsBoundByIndex[i]
if textField.exists && textField.isHittable {
textField.tap()
} else {
// text field is not hittable or doesn't exist!
XCTFail()
}

Answer 2

You shouldn't need to try-catch finding elements in UI Testing. Ask the framework if the element exists() before trying to tap() it.
let app = XCUIApplication()
let element = app.staticTexts["item"]
if element.exists {
element.tap()
} else {
NSLog("Element does not exist")
}
Check out my blog post on getting started with UI Testing for more specific examples, like tapping an button.