ios - Int() 类型转换时 Playground 执行失败

Question

当我遇到这个问题时，我正在使用 Swift 编写本教程。

代码:

var languagesLearned: String = "3"
if let num: Int? = Int(languagesLearned)
{
    print("It is a number")
}
else
{
    print("It is not a number")
}

错误:

Playground execution failed: /var/folders/f7/0j8dbxls0kv0l9d6jwk30f2h0000gn/T/lldb/20598/playground134.swift:72:20: error: cannot invoke 'init' with an argument of type '@lvalue String'
if let num: Int? = Int(languagesLearned)
                   ^~~~~~~~~~~~~~~~~~~~~

我找不到任何关于为什么我会收到这种错误的信息。我也不知道它在说什么 init。

回答后更正代码

var languagesLearned: String = "3"
var languagesLearnedNum = languagesLearned.toInt()
if let num = languagesLearnedNum
{
    print("It is a number")
}
else
{
    print("It is not a number")
}

Answer 1

在 Swift 1.x 中，使用:

languagesLearned.toInt()