[英]'[String]?' does not have a member named 'count' in Swift
我有以下快速代码:
var Data = ["first" : ["Rob ", "Gladys", "Hugh"],
"last" : ["Banks", "Friday", "Mungus"]
]
var elementCount = 0
var key = "first"
var elements = data[key!]
elementCount = elements.count
但是我在此代码的最后一行收到以下错误:
'[String]?' does not have a member named 'count'
如何解决此错误,为什么会发生?
** 编辑 **
如果我还想在特定索引的elements
中提取项目怎么办。 因此,例如:
var myIndex = 1
var firstname = elements[myIndex]
这给出了错误
'[String]?' does not have a member named 'subscript'
此错误意味着您的字典返回了一个可选数组,您需要在尝试访问其属性计数之前将其拆开。 您必须这样做:
let data = ["first" : ["Rob ", "Gladys", "Hugh"],"last" : ["Banks", "Friday", "Mungus"]]
var elementCount = 0
let key = "first"
if let elements = data[key] {
elementCount = elements.count
}
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