如何将ASP.NET Core UserSecrets部署到生产环境(How to deploy ASP.NET Core UserSecrets to production)

 好的，错误说 
 
-[__NSCFString setLinkID:]: unrecognized selector sent to instance 0x6bf37e0
 
 请注意，您以某种方式将setLinkID:消息发送到__NSCFString的实例（基本上是NSString的私有子类）。 
 
 在您的代码中，您只发送setLinkID: to self。 因此，不知何故，您的解析器委托已被解除分配，并且取而代之的是已分配NSString的实例。 
 
 即使您使用ARC，您仍然必须了解对象所有权。 在这种情况下， NSXMLParser不会保留对其委托的引用 ，因为这很可能会创建保留周期。 如果查看标题或文档，您将看到该属性被定义为弱引用。 
 
 我认为正在发生的是你设置了解析器，你没有对主解析器委托的其他强引用，所以在解析开始后不久，它就被解除分配。 您需要浏览代码并确保对该主解析器委托有强引用。 
 
 如果你这样做，你会遇到问题： 
 
NSXMLParser *parser = ...
[parser setDelegate:[[MyParserDelegate alloc] init]];
// delegate immediately deallocated, no strong references to it
if ([parser parse]) {
    MyParserDelegate *delegate = [parser delegate]; // nil or junk at this point
 
 您应该像这样构建代码： 
 
NSXMLParser *parser = ...
MyParserDelegate *topLevelDelegate = [[MyParserDelegate alloc] init];
[parser setDelegate:topLevelDelegate];
if ([parser parse]) {
    // pull data out of topLevelDelegate
 
 如果您在专门的委托中使用交换模式，则topLevelDelegate需要维护对子委托的强引用。 如果您有从子级到父级的强引用，则无关紧要，因为子级本身只能从解析器本身访问，而解析器本身不会保留其委托。 您可能需要两种方式参考：从父母到孩子的强大; 从孩子到父母的弱势。 （通常，此模式将阻止保留周期。） 
 
 哦，回答你的标题问题：是的，ARC可以释放你正在使用的内存，如果它只能通过弱引用来访问它。 但是如果你正在使用它，你应该至少有一个强引用它。 

OK, the error says
 
-[__NSCFString setLinkID:]: unrecognized selector sent to instance 0x6bf37e0
 
Note that you're somehow sending the setLinkID: message to an instance of __NSCFString (basically a private subclass of NSString).
 
In your code, you are only sending setLinkID: to self. So, somehow your parser delegate has been deallocated and, in its place, an instance of NSString has been allocated.
 
Even if you're using ARC, you still have to understand object ownership. In this case, the NSXMLParser does not retain a reference to its delegate, because that would very likely create a retain cycle. If you look in the headers or the documentation you will see that the property is defined as a weak reference.
 
What I think is happening is that you set up the parser, you have no other strong reference to the main parser delegate, so shortly after parsing begins, it is deallocated. You need to go through your code and make sure you have a strong reference to that main parser delegate.
 
You will have problems if you do this:
 
NSXMLParser *parser = ...
[parser setDelegate:[[MyParserDelegate alloc] init]];
// delegate immediately deallocated, no strong references to it
if ([parser parse]) {
    MyParserDelegate *delegate = [parser delegate]; // nil or junk at this point
 
You should structure your code like this:
 
NSXMLParser *parser = ...
MyParserDelegate *topLevelDelegate = [[MyParserDelegate alloc] init];
[parser setDelegate:topLevelDelegate];
if ([parser parse]) {
    // pull data out of topLevelDelegate
 
If you use the pattern of swapping in specialized delegates, the topLevelDelegate needs to maintain a strong reference to the child delegates. If you have a strong reference from the child to the parent, it won't matter, because the child itself will only be reachable from the parser itself, which doesn't retain its delegate. You will probably need a reference both ways: strong from parent to child; weak from child to parent. (In general, this pattern will prevent retain cycles.)
 
Oh, to answer your title question: Yes, it's possible for ARC to release memory you are using, if it is only reachable by weak references to it. But if you're using it, you should have at least one strong reference to it.