Swift：如何解析数字字符串时捕获异常？ [英] Swift: How to catch exception when parsing a numeric string?

问题描述

在C＃或Java中，通常分析数字字符串会引发格式异常。但是，以下代码未捕获此错误。

In C# or Java, usually parsing a numeric string throws a format exception. However, the following code did not catch the error. What is wrong?

func getInt(_ data:String)->Int
{
    do
    {
        return try Int(data)!
    }
    catch
    {
        return -1;
    }
}

var a = "x123"
var b:Int = getInt(a)
print("Result: " + b)

推荐答案

在Swift中，只能使用扔可以接住。 Int 初始值设定项不会抛出

In Swift only methods which can throw can catch. The Int initializer does not throw

Swift模式是可选的

The Swift pattern are optionals

func getInt(_ data:String) -> Int?
{
    return Int(data)
}

let a = "x123"
if let b = getInt(a) {
    print("Result: \(b)")
} else {
    print("No result")
}

或者您可以返回非可选值，并使用nil合并运算符处理可选的 error

Or you can return a non-optional and handle the optional error with the nil coalescing operator

func getInt(_ data:String) -> Int
{
    return Int(data) ?? -1
}

let a = "x123"
let b = getInt(a)
print("Result: \(b)")

或使您的方法可以抛出

enum MyError : Error {
   case conversionError
}

func getInt(_ data:String) throws -> Int
{
    guard let result = Int(data) else { throw MyError.conversionError }
    return result

}

let a = "x123"
do { 
    let b = try getInt(a)
    print("Result: \(b)")
} catch MyError.conversionError {
    print("Could not convert the string '\(a)' to integer")
} 

请阅读快速语言指南

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