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This article is to share with you about the differences between C++ structures and classes. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Struct in C++ extends the struct in C #. It is no longer just a data structure containing different data types, it has acquired too many functions.

Can struct include member functions? Yes!

Can struct inherit it? Yes!

Can struct be polymorphic? Yes!

Since it can do all this, what's the difference between it and class?

One of the most essential differences is default access control:

Default inherited access: struct is public, class is private.

We can write the following code:

Struct A {char a;}; struct B: a {char b;}

At this time, B is inherited by public.

If the above struct is changed to class, then B is inherited from A by private. This is the default inherited access.

So when we usually write about class inheritance, we usually write:

Class B: public A

This is to indicate that it is public inheritance, not the default private inheritance.

Of course, whether public inheritance or private inheritance is the default depends on the subclass, not the base class.

Struct can inherit class, and class can also inherit struct, so the default inheritance access depends on whether the subclass uses struct or class.

As follows:

Struct A {}; class B: a {}; / / private inherits struct C: B {}; / / public inherits

Struct as the implementation of the data structure, its default data access control is public, while class as the implementation of the object, its default member variable access control is private.

I still emphasize that struct is an implementation of data structures, although it can be used in the same way as class. I still call variables in struct data and variables in class members, although there is no difference between them.

Whether to use struct or class, it all depends on your personal preference. You can replace all the class in the program with struct, and it can still run normally.

But the advice is: when you think what you need to do is more like a data structure, then use struct, if you want to do more like an object, then use class.

Of course, I would also like to emphasize here that access control should be clearly pointed out in the program, rather than relying on default, which is a good habit and makes your code more readable.

At this point, many people who know about it may think that this topic is over, because they know that the "only" difference between struct and class is access control. It is true that only this difference is mentioned in many documents.

But I do not use the word "unique" above, but rather the "most essential". That is because they do have another difference, although we may seldom touch on that difference.

This is the end of the discussion. Basically, it should be over. But someone once said that he had found other "differences", so let's see if this is another difference. As mentioned above, the struct in C++ is an extension of struct in C. since it is an extension, it should be compatible with all the features that struct should have in C in the past.

For example, you can write:

Struct A / / defines a struct {char C1; int N2; double db3;}; AA = {'paired, 7, 3.1415926}; / / assigns values directly when defined

In other words, struct can be defined with {} to assign an initial value. So the question is, can class do it? Change the above struct to class and try it. Report a mistake! Oh ~ so the man jumped out and said that he had found another difference. Let's take a closer look, is this really another difference?

We can try to add a constructor (or virtual function) to the above struct, and we will find that struct can no longer assign initial values with {}.

Indeed, assigning initial values in the form of {} only initializes the data sequentially with an initialization list, for example, if it is written as AA = {'paired journal 7} above, then C1 Personnal N2 is initialized, but db3 does not. Such a simple copy operation can only occur on a simple data structure, not on an object. Adding a constructor or a virtual function makes struct more object-specific and makes this {} operation no longer valid.

In fact, it is the addition of such a function that changes the internal structure of the class. What about adding a normal member function? You will find that {} is still available. In fact, you can understand an ordinary function as an algorithm for data structures, which does not break the characteristics of its data structures.

So, seeing here, we find that even if struct wants to assign initial values with {}, it must meet a lot of constraints, which actually make struct more of a data mechanism than a class.

So why can't we just change struct to class and {} can't use it?

In fact, the problem happens to be what we talked about before-- access control! Look, what have we forgotten? Yes, when you change struct to class, the access control changes from public to private, so of course you can't assign an initial value with {}. Add a public and you will find that class can also use {}, which is no different from struct!

To sum up, from the above differences, we can see that struct is more suitable as an implementation of a data structure, and class is more suitable as an implementation of an object.

Thank you for reading! This is the end of the article on "what are the differences between C++ structures and classes". I hope the above content can be of some help to you, so that you can learn more knowledge. If you think the article is good, you can share it for more people to see!

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