如何清理XCUIElement哪个类型是textField？

XCUIElement *textField = app.textFields[@"xxxxx"];
[textField tap];
[textField typeText:@"12345678910"];
XCUIElement *key = app.keys[@"xx"]; (the "xx" is delete key)
    for (int a=0; a<11; a++) {
        [key tap];
    }
XCUIElement *textField = app.textFields[@"xxxxx