CLASSES vs STRUCTS in C++
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- Опубліковано 26 вер 2024
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When I was taking my first class on object oriented programming the teacher showed us classes and I was like "Oh so is this the same thing as a struct?" and she said no without explaining more. I'm glad to see this video lol.
Oh my god, this brings back nightmares of Uni. I program in C++ using a mostly C style structure. Always have. It makes more sense to me, and I don't believe in the bull of having to protect you from yourself (The primary purpose of Private Variables)
I basically said the same thing to my teachers, and they also just say no, without elaboration. After more discussion over the years I was there, I can only gather that the world as a whole prefers Classes because of Private Variables mostly as a protective layer to stop you interfering with a variable you didn't mean to. Which is absolutely ridiculous. Because you simply shouldn't be accessing random variables for no reason while you program. Otherwise, what the hell are you doing?
@@MOWAuthor I also don't really get the purpose of hiding variables from yourself either. Maybe in team projects where you don't trust your fellow programmers and you want to make sure a certain piece of data is handled correctly lol so you just give them functions.
@@MOWAuthor well I think it's more of a "prevention is better than cure" kind of thing. Tbh I get what you're saying but it's more of a preference thing, so to say it's somewhat "ridiculous" is kinda not really unless you mean it only from your standpoint and persons who share it also
Paying $$$ for an education that fails. How many times have I experienced that?
@@RandomUser2401 I don't think so but I may be wrong. There's plenty of ways to implement unintended behavior in C.
love that chicken in the background
I think he's really a New Zealander...
@@treyquattro Hey...? It would be a sheep in that case :D
his whole room decoration is great
I watched through the entire video without noticing that XD
I agree. And also the human who is speaking is interesting to listen to.
To elaborate more on what Cherno says in this video, structs are a legacy feature from C which can group together variables into a user-defined type, BUT CANNOT contain functions (because C did not have OOP features such as methods).
This is why it's common in C++ to use structs for "classes with no methods", because that was how they were used in C.
C++ structs can contain functions.
@@1apostoli Yes, they were talking about C.
when you know java structure and reading this, it is somehow funny and amazing how languages grew and become more useful and flexible😅
@@jazzfan67 yeah. C is awesome. There’s always a simple workaround.
but you can just make functions that operate on structs giving you something verry similar to classes.
the real difference is scope (private members) and inheritance
#define struct class
yeah that's not going to confuse anybody
I actually got it right off the bat without having heard of that before, but that's just me.
Well yes, but actually no
Bruh.....
Dam
that was funny Xd
For anyone struggling with: #define struct class
Basically what he did there is he told the compiler to treat "struct" as a "class".
For example u could do same thing to types like this: #define INTEGER int
And you still could instatiate "INTEGER" the same way you would do it for ""int".
INTEGER a = 8;
==============
is same as:
==============
int a = 8;
Hope that explains it.
Just one confusion here, if we #define struct class wouldn't the code break because of the default visibility difference between them? For example if there is an struct Vec2 and we are using the x coordinate like:
struct Vec2
{
float x, y;
};
struct Vec2 vector;
vector.x = 5.0;
Then this will surely throw an compile error. Please explain it to me if you know the answer otherwise I will make this comment global.
@@twitchoff1114 Yes its just as you said. You would get compiler error if you were to do that.
ty
Subtitles again, "Hey little guys and my name is Machado and welcome to my people of clock series"
LOL!
You know if you have the time, you can manually add the _correct_ subtitles by clicking the settings gear -> subtitles/cc -> add subtitles/cc.
I went ahead and did it for this video since I had time.
Andrew Mitchell thank you. I believe, there have to be more people like you.
@@markeyboi6545 thanks for ruining the funny meme.
the auto generation captions are hilarious
"he little guys my name is Machado and welcome back to my people of clock series"
I'm coming from the world of C#, and I remember that in C#, classes are reference types while structs are value types.
the same as Swift, but it seems C++ is different
MR MEME Thanks for the reply. I am quite clear about this now, after 2 months study. 😉
Yeah, it caught me off guard when he didn't mention this. I guess there is that big difference between C# and C++.
i come from C background and Classes is just a Struct that use functions, but now Struct uses functions too so they made them the same.
Also in C#, with structures, you are forced to initialize all your fields in the constructor so you don't have uninitialized variables
This is a WONDERFUL series. I'll definitely be supporting on patreon
Thanks! By supporting him, you are indirectly supporting many other people that learn from him.
I see some people stating that one additional "difference" between structs and classes is that the structs are stack-allocated and classes are heap allocated. This may be true in languages like C#, however in C++ you may allocate classes (objects, actually) and structs in either the stack or the heap, it's just done differently in code (to allocate on the heap, you use the keyword "new").
You may as well have stack-allocated classes and heap-allocated structs; as Cherno says, there are very few rules in C++ when it comes down to it.
OMG He's not Indian
Finally!
buwahahahahaha but I am. you can't get rid of us. never!
I just wonder why there are so many of you. Do indians love sex so much or something? Is there some kind of Sex religion that makes people make alot of kids? Just wondering.. I don't really have anything against Indians. :)
Herman Williams large numbers gives rise to even larger numbers. And in India people religiously give birth to kids at least 2 per family. And during the 50s to 80s most Indians had more than 3 kids per family. Previously most of the children would die because of disease, malnutrition etc. But after independence and advancements in science the deaths decreased but people still gave birth more children thinking most of them won't survive. We took some time to adapt. Now I think its around 2 per family. Hence the population explosion.
Haha, I feel you bro!
every time I watch a video on your channel, I learn something new that sticks in my head forever.
#Define struct class. That one is mind-blowing!
I just realized you were talking about inheritance and I remember what it was like all those years ago when I first heard the word.
Most people feel the same way: What in the world is inheritance?
Inheritance is probably one of the most useful benefits to classes you have available to you, to allow a class to "inherit" the public members and methods of another class.
They also allow for virtual methods in the base class that all inherited classes has the option of overloading (basically means to re-define), to give them unique functionality.
They are incredibly powerful, and I cannot imagine a world without them.
We use them everywhere in c#, I assume c++ is no different.
Hey Cherno, would you mind making an episode explaiing a bit how char, char static arrays, char dynamic arrays, strings, string arrays etc. work in C++ and when to use which one? I've always found this whole confusion very difficult to deal with.
I find that for the most part, just using std::string is a safe bet. (But I doubt this comment is very helpful..)
I am addicted to learning c++ right now thanks to you.
count me in
After so many years just learned that structs in C++ can have functions. May have seen this in code many times, but never thought they were structs.
Gotta be honest. I've only ever used structs in C programming. Didn't even think about using them in C++. Good to know I wasn't missing anything.
Struct is a Value Type, Class is a Reference Type. Meaning Struct is kept in Stack Memory and a Class only keeps a reference in the Stack (rapid access memory) and the actual content in the Heap Memory. Assigning a variable containing a Struct to another, copies the whole Struct, as contrary to variables containing Classes, that only the referene is copied (meaning pointer, mem address)
Not in C++
The C++ Core Guidelines C.2 states: "Use class if the class has an invariant; use struct if the data members can vary independently."
So if you don't have any preexisting style, your best bet is to stick to that.
@Over Yonder perhaps something to do with OOP features like inheritance, polymorphism, etc?
i think they mean private variables when they say invariant
Invariants are conditions that must hold true for the object of a class to have valid functionality during its lifetime - basically, its when something has to rely on a set of presuppositions to work right.
That’s my understanding after a google search, idk, I’m no software engineer
@@unknownbutawesome8759 these are exactly same for classes and structs. And you can inherit one from the other easily too.
@Over Yonder Usually, we use structs for "combinations of data". And according to Google style, structs should not have methods, they're just something like basic types that have no complex behaviors.
So, for example, if I just want to make the code clearer and more readable, I'll choose write a struct rather than many variables (just like choosing an array instead of many variables):
struct Student {
std::vector scores;
std::string name;
};
Dude, thank you so much holy hell--I've been looking all morning.
TL;DR
Use structs for small stuff, classes for big bois
There is no difference. Structs can inherit from classes, and vice versa. They are the same. Only difference is the default visibility. Struct contents are public by default, class is private.
He obviously knows that, he's in the comments of a dude saying that for 8 mins
@@marekgrencstein7215 It's the same, but there are conventions.
I use structs when i dont need methods. I also dont use contrusctors in a struct. Maybe because I learned C first for me structs are just a container of objects. Or writing C-Style (functional) code and using benefits of C++ like no need of typedef, overloading functions etc..
TL;DL - too long didn't listen
*My takeaways:*
1. The only difference between classes and structs 0:47, by default, the classes are private but the structs are public
2. When to use class and when to use struct 3:35, basically Cherno says that he uses struct just to struct data, and if he needs more functionalities and inheritance, he uses class
Nice notes!
I'd probably limit struct to data types where they only need to supply basic operator functions.
Commenting for your exposure. The best channel on UA-cam for C++ !!!
The difference in default access also applies to inheritance:
struct Foo : Bar // Bar is a public base class of Foo
class Foo : Bar // Bar is a private base class of Foo
Honestly one of the best videos I've seen on this specific topic.
Keep up the good work dude!
haven't watched any of your previous videos but after just watching 3 minutes of this video I came to understand that you are just awesome teacher. Really appreciate your approach.
I'm sure this the only channel that I would actually notice if you went through a weekend without posting one video.
I'm looking forward for the more advanced videos. Thank you.
I don't know why, but yours & mine thinking towards the keywords & software design totally match! For eg: the struct keyword for data only, the class keyword for complex works (that's why they are made for)!
Yes, though back in the old (very old) days we created "classes" in C by having pointers to functions in the struct. Now days I use struct to organize data and classes to act upon data. In my world a class may contain a struct but a struct would not contain a class. If that makes sense.
Nice explanation! I do love how your channel covers C++ so well, it's hard to find good channels about this.
Currently trying to wrap my hand around structs and this video clarified way more than cppreference, SO or w3
Thanks bro
i love you by the way, great series, so how i make the difference is if there is just data ( varables with types) with no functions then its a struct, as soon as you add functions then it becomes a class, some how i feel like struct is supposed to be really simple and class is for more complicated things. no matter what if you program you are awesome.
Excellent explanation! I knew that they only differed by private vs public defaults but I wanted to know the usage of a struct over an object! So basically, use struct for creating data structures, use class for creating objects! This was so helpful!
Just learning C++ again .... Spending time understanding the nuances is paying off. Useful vid.
I have seen every video up to now and they help me very much to refresh my out-dated C++ knowledge
Me: Nice. I'll finally learn the difference between a class and struct
Cherno: There's no difference
Me: Now that's a plot twist :o
Liking each and every video before even listening to the whole thing...That good is this series!
You teach me how to do was very simply and fast to understand. Thanks!
Struct is a public class that can't be instantiated. Wow, where have you been all my life? What a great explanation.
Bro, can't believe you're giving this information for free. Thanks!
in C#, the difference is more fundamental: structs are value types, while a class is always a reference type, so anything that modifies the object modifies the original object, as opposed to a struct where it will modify the individual copy.
This is a C++ video, but I thought I would share that little fact. (I'm not an expert, so I might be wrong... A fact check would be appreciated)
You can even make Structs in C# become Reference-type to make things even more versatyle and convoluted LOL.
Then again, the Unity Engine mostly uses Structs instead of Classes so that kind of versatility is needed.
I use structs when I either need C compatibility or when I am using them in only the C way and have no methods or non-public data. Such as the reg struct in PNF. I had a bunch of variables to group as registers in PNF. PNF works like asm code, but its its own type of "register rich" computer.
Hello @The Cherno. May I know if we are allowed not to add (&) to the method Add, like " void Add (const Vec2 other)"? I tested and the result is the same. Why did you use that? Thank you.
Result is the same, but in your case input class/struct is copied whilst with '&' it's taken by reference.
I really like your teaching style, Yan. Love these videos :D
Another great video from you. Now moving along with a better understanding of the differences. A much, MUCH simpler implementation of the two compared to C# where there are massive difference in the two types and the way you use them.
haha nice to see a follow up video; mentioned the structs under the last video and now here we are ^^ awesome
Roxas from Kingdom Hearts teaches C++
i'd forgotten that structs could contain methods
i was assuming that structs were always just plain old data
very useful
many thanks for sharing your knowledge
Amazing Videos - Thank you The Cherno
0:47 or 1:40 the second difference is that you can't use struct in *templates* (only classes allowed) :)
What do you mean? You can definitely use structs with templates.
To be precise I was meant that you can't use word struct in template declaration.
You can write:
template
or
template
but you can't do that:
template
+aPoCoTuToDac that’s true, but in this case class is just synonymous with typename, it’s not really “class” in the traditional sense. I would always write typename instead of class for template arguments anyway, it makes more sense.
yup, but the example with completely valid template declaration (i.e. template ) shows that in C++ words "struct" and "class" are not fully interchangeable.
If you have one such declaration, and you do #define like in 2:56 but otherwise (i.e. #define class struct) you will run into trouble. :)
+aPoCoTuToDac sure, but this video is about classes vs structures, the actual concept, not literally the keyword in every way. Much of C++ is contextual, for example the static keyword.
the simpeliste tutorial in this tutorial series
There would a difference because in C a strict can’t store a method but the closest it can get, I think, is storing a pointer to the function
Personal notes:
-only difference is while class members are private by default, struct members are piblic by default
-the reason it exists in c++ is backwards compatibility since c has structs
-struct mah be preferred by some when it is for so simple use
-struct is ugly for inheritance
you lost me after: #define struct class
Anywhere you wrote _struct_ is replaced by _class_ when the code is actually compiled.
Also, struct inheritance is public by default.
So instead of:
struct s : public a
{
}
You do:
struct b : a
{
}
?
Love this series.
Amazing content, he explained the difference very well!
short and precise, well done!
I use some similar differentation in use between classes and structs.
If the real thing is just "represented" with some details by the data i stored, its a class. If its "defined" by the data stored then its a struct. "Connections between things" are specific cases for me however. Even if you can further describe the same connection with more details, somehow my brain refuses to treat a connection the same if it have any kind of more requirements (even trivial ones) than before. It's always just similar, but not the same. Must be a "bug" in my cognition, but i'm using struct accordingly.
I don´t get the "void Add(const Vec2& other) function... why did he pass it by reference ?? because we don´t manipulate the other variable in this method so the code would be valid without the references ??
loving this series
I don't know why but you are way too much efficient and different from other people teaching C++.
I would use struct just to store variables in structured way, because that is what structures do in C (they doesn't have methods).
it finally makes sense to me now that I understand that structs in c++ are massively different and upgraded from structs in C lol
I like to use structs inside unions to give the variables initial values without a constructor. If I used a class the extra public keyword makes it less of a one line solution.
Structs in general I think look cleaner in unions tbh.
Very nice work !!
Just found your channel and I have to say it's amazing, love your teaching style. I have some very rough basis of programming (mostly C) and every video I'm learning something new. In this case it seems that structs and classes are pretty much the same thing in C++, BUT (just checked online to be sure) structs in C do not allow functions inside, like the methods in classes. I always thought this was the "main" difference between C and C++ (of course there are plenty more, to the point that are considered different languages overall). So I guess in C++ classes and structs are very similar but C structs and C++ structs are quite different? Just to know if I got that right.
Thanks again and keep up the good work (I know this is a quite old video, but I wanted to say it anyway in case you are reading)!
Hi, Cherno, I wanted to ask you a question in c++. When you say 'const char* str', I understand that the pointer's value in this case, is the first character in the string and the last character is a '\0', signalling the ending of the string. But, why do you put const? I also understand that the const means that the memory address is the thing that is constant, not the characters. But, does it matter? When I put 'char* str;' into my code and set it equal to some random text, I get an error, saying that I am putting a
const char*'s value into a char*!! Also, in the Vec2 example, in the 'add' method, you put in ' **const** Vec2& other'. I understand all the pass by reference stuff, but the **const** is what throws me off. What is it for?
Thanks for reading this if you did!
(please give me an answer! (im dying to know!!(uh oh(bracket inception(OOPS)))))
AnimationMan Const comes from constant.
The general logic is to declare variables/pointers/objects as const as much as you can because it provides security and safety for the value. You can change the value of a variable a program uses if you find a vulnerablility to take control. If that variable is declared as const there is nothing you can do even if you could go that deep.
Kinda same logic with final in java.
In his function/method other is used only for reading data and not manipulating them.
Hope this helps :)
AnimationMan The code below demonstrates a solution to your issue. Uncomment to get the error.
#include
#include
void log(const char *str)
{
std::cout
+Jason Koutoulias thanks so much!
because const is constant value and it means that it would not be changed. when you put it in char* str, it a pointer and compiler thinks that somewhere you may change it.
Short answer - Use only class because it can do everything!!
Feels like in case of DDD, classes would be for entities and aggregates whereas structs would be for value objects
Great video, thank you!
It would be super cool if you made a video called something similar to "all c++ keywords and what they do"
Like a reference video that you can look through and be like "oh yeah i dont know how vectors work" and then you could go learn more about vectors for example...
Just one confusion here, if we #define struct class wouldn't the code break because of the default visibility difference between them? For example if there is an struct Vec2 and we are using the x coordinate like:
struct Vec2
{
float x, y;
};
struct Vec2 vector;
vector.x = 5.0;
Then this will surely throw an compile error.
Thanks
Can you do a video on padding and alignment and also things like the pIMPL idiom?
bro the like button glowed when he said like and subscribe
Wait. So c++ has classes making it an oop language. Structs are technically the same with classes. C has structs. But it doesn't have classes. But classes are the same with structs. Wat?
Except they are not (the same). C structs don't have methods.
Me at the start of the video: yelling at the screen that the difference is that classes have methods and structs do not.
Me at 5:34: oh dear god
For me, classes are usually strong enough to have human-like responsibility
while struct is more like a drawer (maybe a smart drawer as you can add some functionality to it)
The Cherno: A clean and neat house decoration
Also The Cherno: Let me put a chicken here.
I found this helpful. Thanks
So I come mainly from Swift, where class and struct are two rather different things. But my idea of what the difference should be, based on my background in swift, is that a class has identity and a struct does not. So struct Point { x: Int; y: Int } does not have identity, because two points with identical x and y values are in every aspect, identical. If I return you one or the other it doesn't really matter. It's a value type essentially.
A Player object: class Player { p: Point } even if it effectively holds the same data as the Point struct now effectively has identity when we think about it and will, in Swift, act as a reference type
So to summarize: a struct is just the class' little brother whom doesn't have to take as much responsibility.
I feel offended
Classes and structs are very similar and the only technical difference is that classes are private while structs are public.
It boils down to organizing our thought with a redundant piece of functionality in C++.
The way I see it, structs are groups of variables and functions that support a standalone concept like a vector or maybe a data structure. A class should be a noun like a player or a map.
Rules:
* It has to be a class if you are inheriting something.
* It has to be a struct if you are use C
* If you are inheriting something and using C... stop and think about your choices in life.
Thanks Dude! Very helpful!
OMG!! I would like to like this video 10 times but unfortunately, it's not possible!
Such a useful video, Thanks so much!
That's fuckng good
and not getting cencored from some moderator... absolutely great.
Then I am on the right track it seems trying to grasp structs a bit better. I work in Unreal Engine a lot. In UE a struct defined in Blueprints is only able to contain variables, not functions. In UE C++ however they can just like in ordinary C++ also contain functions. Recommended just as shown here are then I guess functions only related to these specific variables like constructor + getters and setters. As I get it and as stated in the video structs are mostly used for grouping variables together for organisation and the actual program logic should be put inside of classes. This is a usage definition I have seen elsewhere also regarding when and how to use classes vs structs. Another thing is that a struct can't be static so they always themselves need to be instantiated somewhere like inside of a class. Therefore they are as I get most useful when u have multiple things all needing the same set of variables like say all the players in a game ect. Players have common variables like heatlh, strength ect. You can thus create a struct called Players and put in variable declarations for health, strength and other player related things . Then each player gets his own instance of that struct like Players Player1; Players Player2; ect and then you can set and get the values for every player like Player1.health = 100, Player2.strength = 50 and so on. The main goal of structs is then as said before organisation of data. Instead of having loose variables everywhere u group them together with a struct related to that particular object type. That is so far how I understand structs should be used. Correct me if im wrong. :)
I always thought that the implementation of struct in C didn't allow for method declaration and that is how I always saw as the major definition between struct and class. Now, I am totally bewildered, help anyone
Thanks a lot, Cherno.
thank you share~
Awesome video as always, but omg what is the song in the beginning? Would really appreciate if someone could tell me.
question is like asking what is the difference between an Object literal and a Class in js lol
Is it possible to declare functions in C structs? I thought it wasn't, but now I am confused. I think that this is possible in C++, but not in C.
You can, however, declare pointers to functions in structs in C
yeah I tried in C 98 version but it threw an error. However when I just changed the file extension to C++ it somehow worked
This is absolutely mind blowing! I didn't know structures can contain function.
I always thought that structures can contain data whereas classes can contain data as well as functions. I guess that's the way I was taught in high school.
HE BLINKED!
Thanks Cherno
Im new to c++ so this might be a stupid question, but a method is basically nothing else than a function within a class or structure, right?
Also: If you keep it really simple (by that i mean simple, as it would probably never ever be in "real" code) you could also substitute some classes with just functions, cant you? (void functions)
I have a question, not really around the topic
in 5:41
he wrote void Add(const Vec2& other) ...
why is it const and why is there '&'? Is it like a pointer to the original vector?
It's reference to the other vector but I also don't understand why it is there, beacouse Adding vectors in this context doesn't change other vector. He even uses const to make sure not to change other vector. so I think that void Add(const Vec2& other) would act the same as void Add(const Vec2 other), and beacouse if we don't pass by reference it would work without const by implicitly. Or I don't understand something.