变量是写的,但从未读过？

Question

我variable 'isTaken' was written to, but never read在以下代码上收到以下警告:

func textFieldShouldEndEditing(textField: UITextField) -> Bool {

        var isTaken: Bool = false

        if textField == usernameTxt { var query = PFQuery(className: "_User")
        query = PFQuery(className: "_User")
        query.whereKey("username", equalTo: usernameTxt.text!)
        query.findObjectsInBackgroundWithBlock {
            (objects: [AnyObject]?, error: NSError?) in
            if error == nil {
                if (objects!.count > 0){

                    isTaken = true

                    }
                } else {
                    print("Username is available. ")
                }
            } else {
                print("error")
            }
          }
        }
        return true
    }

为什么我会收到警告,如何取消它？

Answer 1

正如错误所示variable 'isTaken' was written to, but never read意味着您正在创建isTaken实例并为其分配值但它从未使用过.

Answer 2

只需删除以下语句：

var isTaken: Bool = false
isTaken = true

由于从未使用过该值，因此定义和分配给if不会产生任何效果。