如何继承NSDictionary? [英] How to inherit from NSDictionary?
问题描述
我有一个名为设置"的对象,该对象继承自NSMutableDictionary
.当我尝试使用
I have an object called Settings that inherits from NSMutableDictionary
. When I try to initialize this object using
Settings *settings = [[Settings alloc] initWithContentsOfFile: @"someFile"]
它返回类型为NSCFDictionary
的对象.结果,它无法识别我的其他方法.例如,当我将选择器称为保存"时,它会对象:
it returns an object of type NSCFDictionary
. As a result, it doesn't recognize my additional methods. For example, when I call the selector "save", it objects:
[NSCFDictionary save]: unrecognized selector sent to instance 0x524bc0
当然,当我使用花园品种进行初始化时就可以了
Of course, it's OK when I initialize using the garden variety
Settings *settings = [[Settings alloc] init]
我试图再次将其投射到设置",但这没有用.这似乎很简单-我想念什么?
I tried to cast it again to Settings but that didn't work. This seems really simple - what am I missing?
谢谢
推荐答案
NSDictionary是一个类集群.这意味着从其init方法返回的值严格来说不是NSDictionary,而是实现实际功能的子类.在几乎每种情况下,最好给您的类一个NSDictionary作为实例变量,或者只在NSDictionary上定义一个类别.
NSDictionary is a class cluster. This means that the value returned from its init methods is not strictly an NSDictionary, but a subclass that implements the actual functionality. In almost every case, it is better to give your class an NSDictionary as an instance variable or to simply define a category on NSDictionary.
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