Question

Swift新手在这里尝试设置数据验证功能，但我的代码生成以下错误：“二元运算符'＆gt;'不能适用于两个'双？'操作数“

func validateDouble(text: String) -> Bool {
    var result = false

    // test input to see if it is a positive Double once text is converted
    if Double(text) > 0.0 {
        result = true
    }
}

我很难过，希望得到任何帮助。

谢谢，

NAS

Answer 1

因为当你将字符串转换为Double类型时它返回可选值，所以它可能是零或不是。这就是为什么不能与精确值进行比较的原因。试试这种方式。

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Answer 2

你需要检查确保转换后的值不是nil，这应该可以解决问题：

func validateDouble(text: String) -> Bool {

    // test input to see if it is a positive Double once text is converted
    guard let value = Double(text), value > 0.0 else { return false }
    return true

}

Answer 3

试试这个

if let doubleValue = Double(text), doubleValue > 0.0 {
  result = true
}

初学者Swift 3数据验证

3 个答案: