Swift中的Error

OC中的错误是一个类NSError：

// Immutable, and NSError must be Sendable because it conforms to Error in Swift
open class NSError : NSObject, NSCopying, NSSecureCoding, @unchecked Sendable {

    
    /* Domain cannot be nil; dict may be nil if no userInfo desired.
    */
    public init(domain: String, code: Int, userInfo dict: [String : Any]? = nil)
    ....
}

而Swift中的错误则是一个协议Error：

public protocol Error : Sendable {
}
public protocol Sendable {
}

extension Error {

    /// Retrieve the localized description for this error.
    public var localizedDescription: String { get }
}

extension NSError : Error {
}

实际上这个协议没有任何内容，因此任意类、结构体、枚举都可以轻松实现Error协议。

定义Swift Error:

使用枚举

enum NetworkError: Error {
    case domainError
    case decodingError
    case noDataError
    
    var localizedDescription: String {
        switch self {
        case .domainError:
            return "url错误"
        case .decodingError:
            return "解析出错"
        case .noDataError:
            return "无数据"
        }
    }
}

由于错误一般是后台接口给出，所以个人觉得使用结构体表示错误，使用是最方便的：

struct BusinessError: Error {
    var code = ""
    var message = ""
    
    init(code: String, message: String) {
        self.code = code
        self.message = message
    }
    
    var localizedDescription: String {
        return message
    }
}

如果需要具体判断错误码，可以扩展BusinessError，不同的业务接口可以创建不同的扩展。

extension BusinessError {
    struct SuperLike {
        static let unknow = ""
        static let badParam = "-10000"
        static let badGender = "-10001"
        static let notMatch = "-10002"
        static let overFrequent = "-10003"
    }
}

func estimateErr() {
    if error.code == BusinessError.SuperLike.badParam {
        print("badParam")
    } else if error.code == BusinessError.SuperLike.badGender {
        print("badGender")
    }
}