38 lines
1.0 KiB
Markdown
38 lines
1.0 KiB
Markdown
---
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title: Error Handling
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---
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# Error Handling
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You represent errors using any type that adopts the `Error` protocol.
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```Swift
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enum PrinterError: Error {
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case outOfPaper
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case noToner
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case onFire
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}
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```
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Use `throw` to throw an error and `throws` to mark a function that can throw an error. If you throw an error in a function, the function returns immediately and the code that called the function handles the error.
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```swift
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func send(job: Int, toPrinter printerName: String) throws -> String {
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if printerName == "Never Has Toner" {
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throw PrinterError.noToner
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}
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return "Job sent"
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}
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```
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There are several ways to handle errors. One way is to use `do`-`catch`. Inside the `do`block, you mark code that can throw an error by writing `try` in front of it. Inside the `catch` block, the error is automatically given the name `error` unless you give it a different name.
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```swift
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do {
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let printerResponse = try send(job: 1040, toPrinter: "Bi Sheng")
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print(printerResponse)
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} catch {
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print(error)
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}
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// Prints "Job sent"
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```
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