如何声明返回基类的方法(how to declare method which returns base Class)

如何声明返回基类的方法(how to declare method which returns base Class)

我想添加一个返回Class的方法，如下所示：

-(Class) validatorClass{

return [AddItemValidator class]; }

并像这样使用它：

self.validator = [[self validatorClass] alloc] initWithParentDirectory:self.parentDirectory];

我应该如何声明此方法的返回类型-(Class)以允许仅返回从定义的类扩展的类？

我想返回类似-(Class<'NameValidator'>) ，其中AddItemValidator从NameValidator扩展。

我该如何申报？

I would like to add a method which returns Class like below:

-(Class) validatorClass{

return [AddItemValidator class]; }

and use it like this:

self.validator = [[self validatorClass] alloc] initWithParentDirectory:self.parentDirectory];

How should I declare the return type -(Class) of this method to allow returning only classes which extend from defined class?

I would like to return something like -(Class<'NameValidator'>) where AddItemValidator extends from NameValidator.

How should I declare it?

最满意答案

正如SomeGuy所提到的，在这种情况下你无法实现编译时的安全性。 相反，您可以使用断言在运行时检查它（总比没有好）：

-(Class) validatorClass{ Class theClass = [AddItemValidator class]; NSAssert([theClass isSubclassOfClass:[NameValidator class]], @"Has to return subclass of %@", [NameValidator class]); return theClass; }

您甚至可以进一步在此处应用Factory模式，以将验证器类与正在验证的类分离：

@implementation NameValidatorFactory +(NameValidator*)validatorForObject:(YourObjectType*)validatedObject { //choose proper validator depending on your object's type or anything you want if([validatedObject isKindOfClass:[YourObjectTypeSuperclass class]]) { return [AddItemValidator alloc]; } else { // handle other cases } }

然后创建你的验证器：

self.validator = [[NameValidatorFactory validatorForObject:self] initWithParentDirectory:self.parentDirectory];

As SomeGuy mentioned, you can't achieve compile-time safety in this case. Instead, you can use an assertion to have it checked at the runtime (better than nothing):

-(Class) validatorClass{ Class theClass = [AddItemValidator class]; NSAssert([theClass isSubclassOfClass:[NameValidator class]], @"Has to return subclass of %@", [NameValidator class]); return theClass; }

You can even go further and apply Factory pattern here to decouple validator class from the class being validated:

@implementation NameValidatorFactory +(NameValidator*)validatorForObject:(YourObjectType*)validatedObject { //choose proper validator depending on your object's type or anything you want if([validatedObject isKindOfClass:[YourObjectTypeSuperclass class]]) { return [AddItemValidator alloc]; } else { // handle other cases } }

And then create your validator like that:

self.validator = [[NameValidatorFactory validatorForObject:self] initWithParentDirectory:self.parentDirectory];