零合并运算符错误 "Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)'"

Question

我收到 nil-coalescing 运算符的错误 "Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)'"。

stackoverflow上也有类似的问题，但是没有给我需要的解决方法

我的代码在注释中有错误：

let cell = tableView.dequeueReusableCell(withIdentifier: "countCell", for: indexPath)
cell.textLabel?.text = String(detailItem?.count) ?? "1" // Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)'

let cell = tableView.dequeueReusableCell(withIdentifier: "countCell", for: indexPath)
cell.textLabel?.text = String(Int(detailItem?.count)) ?? "1" // Cannot invoke initializer for type 'Int' with an argument list of type '(Int64?)'

let cell = tableView.dequeueReusableCell(withIdentifier: "countCell", for: indexPath)
cell.textLabel?.text = String(Int(detailItem!.count)) ?? "1" // Cannot invoke initializer for type 'Int' with an argument list of type '(Int64?)'

let cell = tableView.dequeueReusableCell(withIdentifier: "countCell", for: indexPath)
cell.textLabel?.text = String(detailItem?.count ?? "1") // Cannot convert value of type 'String' to expected argument type 'Int64'

Answer 1

你可以简单地做，

let int64Value: Int64 = 123
let str = String(int64Value)

编辑：

因为 detailItem?.count 是 optional，你需要 unwrap 它传递给 String initializer。您可以使用 nil 合并运算符 展开并提供默认值，即

cell.textLabel?.text = String(detailItem?.count ?? 1)

Answer 2

let tmp = Int64(10)
print(String(tmp))

零合并运算符错误 "Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)'"

Error "Cannot invoke initializer for type 'String' with an argument list of type '(Int64?)'" with nil-coalescing operator

int64

swift