Question

 func buttonAction(sender:radioButton!) {
    let tempGetTestDesc = dspResult[sender.indexPathSection!]["tests"] as! NSMutableDictionary
    let temp = tempGetTestDesc["tests"]as! NSMutableArray
    var tem = temp[sender.indexPathRow!] as! Dictionary<String, AnyObject>
 switch sender.tag{
    case 110:
        tem["sideValue"] = "Left"
    case 111:
         tem["sideValue"] = "Right"
    case 112:
          tem["sideValue"] = "Both"
    case 113:
        tem["contrastValue"] = "Y"
    default:
        break
    }

它不会导致上述代码出错。但是它没有更新dspResult中的值。它只更新tem内的值。所以我使用以下代码来更新值。

(((dspResult[sender.indexPathSection!]["tests"] as! NSMutableDictionary)["tests"]as! NSMutableArray)[sender.indexPathRow!] as! Dictionary<String, AnyObject>)["contrastValue"] = "Y"

但是，它不起作用。无法分配类型为

的不可变表达式

Answer 1

原因是你将tem变量打开为Dictionary，swift中的Dictionary是value type，这意味着，任何变量赋值都会导致创建一个新的字典对象并赋值变量，而不是引用赋值。

 func buttonAction(sender:radioButton!) {
    let tempGetTestDesc = dspResult[sender.indexPathSection!]["tests"] as! NSMutableDictionary
    let temp = tempGetTestDesc["tests"]as! NSMutableArray
    var tem = temp[sender.indexPathRow!] as! NSMutableDictionary // <--- Instead of Dictionary
 switch sender.tag{
    case 110:
        tem["sideValue"] = "Left"
    case 111:
         tem["sideValue"] = "Right"
    case 112:
          tem["sideValue"] = "Both"
    case 113:
        tem["contrastValue"] = "Y"
    default:
        break
    }

您可以将以下代码复制并粘贴到游乐场，您就会明白我的意思。

let a = NSMutableDictionary(dictionary: ["a": 1])
let aa = NSMutableArray(array: [a])
var b = aa[0] as! Dictionary<String, AnyObject>  // <-- b is a new copy of a dictionary, so change the value in b, will not impact to the variable a
b["a"] = 2 
print(a["a"]!)

let c = aa[0] as! NSMutableDictionary // <--- c is reference to the origin dictionary a, so changing the value in c will change the value in a
c["a"] = 2
print(a["a"]!)

无法分配给类型的不可变表达式

1 个答案: