swift - 无法快速增加数字

Question

我有一个从 keystore 填充的变量，当它递增时，会给出一个错误，内容如下:“NSNumber 不可转换为@lvalue UIint8”

if let bankbalance: AnyObject? = keystore.objectForKey("coinbalance"){
   let mybalance = bankbalance as NSNumber
    mybalance += 50 //this line gives the error 
}

我的问题是什么可以转换为 UIint8 以便我可以添加到我的变量中？我试过 INT、Float、double。

Answer 1

你试图给 let 添加一个值，而 let 是一个常量，你不能在初始化后给 let 赋值。

苹果文档:

Constants and variables associate a name (such as maximumNumberOfLoginAttempts or welcomeMessage) with a value of a particular type (such as the number 10 or the string "Hello"). The value of a constant cannot be changed once it is set, whereas a variable can be set to a different value in the future.

var 

是你想要的