在iOS中将对象转换为其子类(Turn an object into its subclass in iOS)

在iOS中将对象转换为其子类(Turn an object into its subclass in iOS)

我有一个Person对象，其中包含name ， email ， birthdate等内容。

我还有一个名为Member的Person子类，其中包含yearJoined ， title等内容。

在我的代码中，如何将现有Person转换为Member ？ 例如：

Member *mem = self.person;

我收到编译错误，因为类不匹配。 但是子类应该继承其父类的所有属性，所以我正在寻找一种方法来说“这个Person对象现在应该是一个Member对象”。

那有意义吗？

I have a Person object which contains things like name, email, birthdate, etc.

I also have a subclass of Person called Member, which contains things like the yearJoined, title, etc.

In my code, how can I take an existing Person and convert it to a Member? For example:

Member *mem = self.person;

I'm getting compiler errors because the classes don't match. But the subclass should inherit all the properties of its parent, so I'm looking for a way to just say "this Person object should now be a Member object."

Does that make sense?

最满意答案

一种方法是在Member类中声明initWithPerson类方法和memberFromPerson静态方法：

@interface Member : Person { NSString *title; ... } - (id)initWithPerson:(Person *)aPerson title:(NSString *)aTitle; + (Member *)memberFromPerson:(Person *)aPerson title:(NSString *)aTitle; @end

在您的实施中：

@implementation Member - (id)initWithPerson:(Person *)aPerson title:(NSString *)aTitle { if (self = [super initWithName:aPerson.name email:aPerson.email birthdate:aPerson.birthdate]) { self.title = aTitle; } return self; } + (Member *)memberFromPerson:(Person *)aPerson title:(NSString *)aTitle { return [[Member alloc] initWithPerson:aPerson title:aTitle]; } @end

然后，当您想将Person实例转换为Member ，您只需要调用：

Member *newMember = [Member memberFromPerson:myPerson title:@"New member!"];

当然，您可以自定义所有这些，具体取决于其他变量（如title或year）是否需要加入（您可以创建memberFromPerson:的版本memberFromPerson:如果正确初始化所有内容，则不需要任何其他参数）。

One way to do that would be to declare an initWithPerson class method and a memberFromPerson static method in your Member class:

@interface Member : Person { NSString *title; ... } - (id)initWithPerson:(Person *)aPerson title:(NSString *)aTitle; + (Member *)memberFromPerson:(Person *)aPerson title:(NSString *)aTitle; @end

And in your implementation:

@implementation Member - (id)initWithPerson:(Person *)aPerson title:(NSString *)aTitle { if (self = [super initWithName:aPerson.name email:aPerson.email birthdate:aPerson.birthdate]) { self.title = aTitle; } return self; } + (Member *)memberFromPerson:(Person *)aPerson title:(NSString *)aTitle { return [[Member alloc] initWithPerson:aPerson title:aTitle]; } @end

Then when you want to convert your Person instance into a Member, you just need to call:

Member *newMember = [Member memberFromPerson:myPerson title:@"New member!"];

Of course you can customize all this depending on how the other variables like title or year joined are required or not (you can create a version of memberFromPerson: without any other argument if you initialize everything properly).