swift - 为什么下面的代码会导致无限递归？

Question

class TestClass : NSObject {

    var definitions: NSSet = NSSet()

    func addDefinitionsObject(value: AnyObject) {
        self.mutableSetValueForKey("definitions").addObject(value)
    }

    func removeDefinitionsObject(value: AnyObject) {
        // this method is never called
        self.mutableSetValueForKey("definitions").removeObject(value)
    }
}

var test = TestClass()
test.addDefinitionsObject("yo")

运行它会导致无限递归，最终会因 EXC_BAD_ACCESS 而崩溃。知道为什么会这样吗？

奇怪的是，只有在定义了 removeDefinitionsObject 时才会发生这种情况。如果我删除该功能，问题就会消失。

Answer 1

来自 "Accessor Search Pattern for Unordered Collections"在《Key-Value Coding Programming Guide》(强调我的):

The default search pattern for mutableSetValueForKey: is as follows:

• Searches the receiver's class for methods whose names match the patterns add<Key>Object: and remove<Key>Object: (corresponding to the NSMutableSet primitive methods addObject: and removeObject: respectively) and also add<Key>: and remove<Key>: (corresponding to NSMutableSet methods unionSet: and minusSet:). If at least one addition method and at least one removal method are found each NSMutableSet message sent to the collection proxy object will result in some combination of add<Key>Object:, remove<Key>Object:, add<Key>:, and remove<Key>: messages being sent to the original receiver of mutableSetValueForKey:.
• ...

这意味着如果addDefinitionsObject和 removeDefinitionsObject在你的类中实现，然后

self.mutableSetValueForKey("definitions").addObject(value)

通话

self.addDefinitionsObject(value)

因此递归。