在 Swift 3 中处理 try 和 throws [英] Handling try and throws in Swift 3

问题描述

在使用 Swift 3 之前:

Before Swift 3 I was using:

guard let data = Data(contentsOf: url) else {
                print("There was an error!)
                return
            }

但是我现在必须使用do、try 和catch.我不熟悉这种语法.我将如何复制这种行为?

However I now have to use do, try and catch. I'm not familiar with this syntax. How would I replicate this behaviour?

推荐答案

这里的区别在于 Data(contentsOf: url) 不再返回 Optional，而是抛出.

The difference here is that Data(contentsOf: url) does not return an Optional anymore, it throws.

所以你可以在 Do-Catch 中使用它，但没有 guard:

So you can use it in Do-Catch but without guard:

do {
    let data = try Data(contentsOf: url)
    // do something with data
    // if the call fails, the catch block is executed
} catch {
    print(error.localizedDescription)
}

请注意，您仍然可以将 guard 与 try? 一起使用，而不是 try，但可能会忽略可能的错误消息.在这种情况下，您不需要 Do-Catch 块:

Note that you could still use guard with try? instead of try but then the possible error message is ignored. In this case, you don't need a Do-Catch block:

guard let data = try? Data(contentsOf: url) else {
    print("There was an error!")
    // return or break
}
// do something with data

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