New knowledge in big homework

C++ Final assignment —— Make a small world

As the builder of the program , I found some problems when writing the framework and adding , And make the following partial solutions .

1、 Use of multiple inheritance

At the beginning, I hope the program can show the characteristics of simplicity , According to the knowledge learned at that time, we finally adopted the method of multiple documents . And when there is no learning inheritance , When I finish compiling some programs of the two classes and prepare for debugging , Find out if main Function is also created Player Class objects and Study Class object , Because attributes exist in various objects , Finally, it is inconvenient to summarize , So I found the method of inheritance . Inheritance can ensure that there is only one object in the whole program , Only the attribute of this object changes . However, there are three classes in this program , Want to make main Only exists in the function Player Class object , You need to let him inherit two classes , Through learning, I learned the mode of multiple inheritance , I found no problem after trying .

2、 Redefining problems （ See the previous blog for details ）

The second problem is to find that when I attach several files with inheritance , The program will report an error , Error name has [Error] previous definition of 'class XXX' as well as [Error] redefinition of 'class XXX', And that is [Error]expected class-name before '{' token, Later, I searched the Internet , It is found that there is a problem of redefinition . Finally, add #ifndef _ Class name _H and #define _ Class name _H, Tail add #endif, According to the information I searched , It roughly means when this macro （define The following identifier ） When it hasn't been defined yet , The preprocessor will insert the contents of the header file , When this macro appears again in the future ifndef Judgment for false, The contents of this header file will not be inserted , That is to avoid redefinition .

3、 How to jump out of multiple cycles

Help fill in 1 In the end , At first, I hope to use break Out of the loop , But because the program is a nested loop , You can only jump one level . So set a global variable , When this ending is triggered, the value of the global variable changes . Set a condition in the outer loop , If the value of the global variable changes, it will jump out of the outer loop . But no matter how you try, the system will automatically trigger the outer layer break, The game went through a month . Finally, when I check the information on the Internet , Found the existence of labels . Finally, I added goto sentence , stay main A label is added at the end of the function , Make this ending jump out of the double-layer cycle at one time , And skip the ending , End the program directly .

4、 similar “ Change the scene ” How to change the page

When I saw the students' very simple pictures in class, I liked them very much , At first, our program didn't have the function of clearing the screen , So the whole program is very lengthy . After class, I checked the relevant information on Friday evening , Used system(“cls”); Statement to clear the previous program . Choose the right time to clear the screen according to the program content . For example, basic options one, two, three , If you choose 1, Go to the classroom , At this time, clear the screen , eject “ Arrive at the classroom ” Words , And then create a sense of the scene when you really arrive in the classroom .

（ Digression ：

It should have been written last month , I felt it , I didn't write an article last month, mainly because of the exam + Big homework is too busy

Because the big homework is the result of the Group , No source code , What you want can be sent by private mail （ Although the things made are not very interesting

This blog is extracted from the report , There may be suspicion that the context is not smooth , Please understand

Please correct me if there is any mistake , Be deeply grateful

）