给出具体实例说明重新定义(redefining)和覆盖(overrinding)有什么不同?
时间: 2023-04-30 11:05:11 浏览: 68
重定义(redefining)和覆盖(overriding)都涉及到类中方法的重写,但它们有所不同。重定义指在子类中重新定义与父类同名的方法,这意味着子类方法的实现与父类不同。而覆盖则指子类继承父类方法并重写该方法的实现。在覆盖中,子类方法的名称、参数类型和返回类型都必须与父类方法相同。
相关问题
#include <stdio.h> #define a 9 #define b 9 #define c 10如何在主函数中自定义更改宏定义
在主函数中无法直接更改宏定义,因为宏定义是在预处理阶段展开的。但你可以在主函数中重新定义另外的常量或变量来达到相同的效果,例如:
```
#include <stdio.h>
#define a 9
#define b 9
#define c 10
int main() {
printf("a=%d, b=%d, c=%d\n", a, b, c);
#undef a
#define a 100
printf("After redefining: a=%d, b=%d, c=%d\n", a, b, c);
return 0;
}
```
在上面的示例代码中,我们使用 `#undef` 取消了宏定义 `a`,然后重新定义为 `100`。这样就可以在主函数中自定义更改宏定义的值了。但是需要注意,重新定义宏定义可能会导致代码混乱,所以应该谨慎使用。
Uncaught TypeError: document. forms is not a function
The error message "Uncaught TypeError: document.forms is not a function" means that you are trying to use the method "forms()" on the "document" object, but it is not a function.
Here are a few possible reasons for this error:
1. The "forms" property may not be defined on the "document" object in your browser or environment.
2. There may be a conflict with another script that is redefining or overwriting the "document.forms" method.
3. There may be a syntax error or typo in your code that is causing the error.
To resolve this error, you can try the following steps:
1. Check your code for any syntax errors or typos that may be causing the problem.
2. Make sure that the "forms" property is supported on the "document" object in your browser or environment.
3. Try renaming the "forms" property to something else to avoid conflicts with other scripts. For example, you could use "myForms" instead of "forms".
4. Try using a different method or property to access the forms on the page, such as "document.getElementsByTagName('form')" or "document.querySelectorAll('form')".
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