Question

由于Swift目前没有try-catch，我怎么能防止这行代码中出现错误数据崩溃？

var myObject = NSKeyedUnarchiver.unarchiveObjectWithData(data) as MyClass

更新

我在操场上创建了一个非常简单的案例进行演示。假设我们不知道data中的内容，我怎样才能在第二行捕获SIGABRT？在调用unarchiveObjectWithData之前，是否无法检查以确保可以取消归档NSData对象？

var data = "foo bar".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!
if let unarc = NSKeyedUnarchiver.unarchiveObjectWithData(data) { // Execution was interrupted: signal SIGABRT
}

Answer 1

我认为现在最好的选择是，在Apple更新NSKeyedUnarchiver的实现以不使用异常或向Swift添加异常支持之前，您将不得不使用Objective-C包装器来尝试捕获。

您可以在此处查看包装器的示例： https://medium.com/swift-programming/adding-try-catch-to-swift-71ab27bcb5b8

基本上，您可以引入一个Objective-C函数或类，它允许您使用Swift中的try-catch块。我喜欢将上面的例子作为初始化程序实现，以使其在Swift中更清晰：

// In Objective-C
// ----------------------

@interface try: NSObject

- (id)initWithTry:(void(^)())try catch:(void(^)(NSException *exception))catch finally:(void(^)())finally;

@end

@implementation try

- (id)initWithTry:(void(^)())try catch:(void(^)(NSException *exception))catch finally:(void(^)())finally
{
    self = [super init];
    if (self) {
        @try {
            try ? try() : nil;
        }
        @catch (NSException *exception) {
            catch ? catch(exception) : nil;
        }
        @finally {
            finally ? finally() : nil;
        }
    }
    return self;
}

@end

// From Swift (make sure you import the objc header in your bridging header
// ----------------------

var data = "foo bar".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!
try(
    try: { () -> Void in
        if let unarc: AnyObject = NSKeyedUnarchiver.unarchiveObjectWithData(data) { // Execution was interrupted: signal SIGABRT
            println(unarc)
        }
    },
    catch: { exception in
        println("Failed to parse data: \(exception)")
    },
    finally: nil
)

NSKeyedUnarchiver错误处理 - 防止Swift崩溃

1 个答案: