由于
Swift目前没有try-catch,我应该如何防止这行代码中的错误数据崩溃？
var myObject = NSKeyedUnarchiver.unarchiveObjectWithData(data) as MyClass
UPDATE
我在操场上创造了一个非常简单的案例来进行演示.假设我们不知道数据是什么,如何在第二行捕获SIGABRT？是否没有办法检查以确保在调用unarchiveObjectWithData之前可以取消归档NSData对象？
var data = "foo bar".dataUsingEncoding(NSUTF8StringEncoding,allowLossyConversion: true)!
if let unarc = NSKeyedUnarchiver.unarchiveObjectWithData(data) { // Execution was interrupted: signal SIGABRT
}
解决方法
我认为现在最好的赌注是,直到Apple更新NSKeyedUnarchiver的实现才能使用异常或者向Swift添加异常支持,您将不得不使用Objective-C包装器来尝试捕获.
您可以在这里看到一个包装器的例子：
https://medium.com/swift-programming/adding-try-catch-to-swift-71ab27bcb5b8
基本上,您可以引入一个单一的Objective-C函数或类,这将允许您使用Swift的try-catch块.我喜欢将上述示例作为初始化器来实现,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
)