从父类方法调用子类的方法（Objective-c 2.0） [英] Calling method on child class from parent class method (Objective-c 2.0)

问题描述

我有面向对象编程的经验，但出于某种原因这种情况并不熟悉。考虑以下Objective-c 2.0代码：

I have experience with object-oriented programming however this situation is unfamiliar for some reason. Consider the following Objective-c 2.0 code:

@interface A : NSObject
@end

@implementation A
- (void) f {
    [self g];
}
@end

@interface B : A
@end

@implementation B
- (void) g {
    NSLog(@"called g...");
}
@end

这是调用方法的正确方法吗父类中的方法的子类？如果另一个子类没有实现方法 g ，会发生什么？也许有更好的方法来解决这个问题，如父类中的抽象方法 A ？

Is this the correct way to call a method on a child class from a method in the parent class? What happens if another child class doesn't implement method g? Perhaps there's a better way to solve this like an abstract method in the parent class A?

推荐答案

关键是在父类中有一个可以在子类中重写的方法。

The key is to have a method in the parent class that may be overriden in the child class.

@interface Dog : NSObject
- (void) bark;
@end

@implementation Dog
- (void) bark {
    NSLog(@"Ruff!");
}
@end

@interface Chihuahua : Dog
@end

@implementation Chihuahua
- (void) bark {
    NSLog(@"Yipe! Yipe! Yipe!");
}
@end

你看，你的子课将覆盖父母方法有自己的实现。您可能会看到它使用如下：

You see, your child class will override the parent method with its own implementation. You might see it used like this:

Dog *someDog = [Chihuahua alloc] init] autorelease];
[someDog bark];

输出： Yipe！沮丧的声音！ Yipe！

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