快速错误处理 - 确定错误类型 [英] Swift error handling - determining the error type
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问题描述
在Swift错误处理中 - 您如何知道在不查看实现的情况下抛出什么错误类型,并且如何处理方法可以抛出ErrorType派生错误和NSError的情况?
In Swift error handling - how do you know what error type is being thrown without looking at the implementation and how do you handle the case where ErrorType-derived error and NSError can be thrown by the method?
例如
代码不显示将会抛出什么类型的错误。
Code does not show what type of error will be thrown.
public func decode(jwt: String) throws -> JWT {
return try DecodedJWT(jwt: jwt)
}
推荐答案
您可以将引发的错误捕获到变量中,并对变量进行运行时分析。例如,一些未知的实现:
You can catch the thrown error to a variable and do runtime analysis of the variable. E.g., for some unknown implementation:
/* ---------------------- */
/* unknown implementation */
enum HiddenError: ErrorType {
case SomeError
}
class AnotherError : NSError { }
func foo() throws -> Int {
let foo = arc4random_uniform(3);
if foo == 0 {
throw HiddenError.SomeError
}
else if foo == 1 {
throw AnotherError(domain: "foo", code: 0, userInfo: [:])
}
else if foo == 2 {
throw NSError(domain: "foo", code: 0, userInfo: [:])
}
else {
return Int(foo)
}
}
/* ---------------------- */
调查错误为:
/* "External" investigation */
func bar() throws -> Int {
return try foo()
}
func fuzz() {
do {
let buzz = try bar()
print("Success: got \(buzz)")
} catch let unknownError {
print("Error: \(unknownError)")
print("Error type: \(unknownError.dynamicType)")
if let dispStyle = Mirror(reflecting: unknownError).displayStyle {
print("Error type displaystyle: \(dispStyle)")
}
}
}
fuzz()
/* Output examples:
Error: SomeError
Error type: HiddenError
Error type displaystyle: Enum
//
Error: Error Domain=foo Code=0 "(null)"
Error type: AnotherError
Error type displaystyle: Class
//
Error: Error Domain=foo Code=0 "(null)"
Error type: NSError
Error type displaystyle: Class */
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