#how to use references (should i be using pointers?)

85 messages · Page 1 of 1 (latest)

safe cradle
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guys im new to cpp and my vscode is yelling at me please help

image.png
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sorry for profanity

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it really doesnt like this move i tried to pull off lol

timid apexBOT
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@safe cradle has reached level 1. GG!

raw thicket
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because you have a reference in your struct

timid apexBOT
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@raw thicket has reached level 2. GG!

raw thicket
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in this case the compiler won't generate assignment operator for you

willow relic
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It’s because of the reference type, from cpp reference:

Deleted copy assignment operator
An implicitly-declared or explicitly-defaulted(since C++11) copy assignment operator for class T is defined as deleted(since C++11) if any of the following conditions is satisfied:
….
T has a non-static data member of a reference type.

timid apexBOT
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@ancient python has reached level 31. GG!

ancient python
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Nice variable name, I cant even type it out

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replace fellow& my_son with fellow* my_son

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& is reference(pointing to temporary object), while * is pointer(pointing always to an object)

velvet steppe
velvet steppe
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@ancient python lol why are you nerd reacting?

ancient python
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wrong word

velvet steppe
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well references reference objects, just like pointers

ancient python
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*excessive

velvet steppe
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l-value references cannot reference "temporary objects" which would be rvalues

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neither can pointers

ancient python
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that what I tried to say

velvet steppe
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pointers specifically can not point to an object, they can be null

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while references are always initialized

velvet steppe
ancient python
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like I thought it is illegal in C++ to have class field like
Something& something;

velvet steppe
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that's perfectly legal

ancient python
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because it is uninitialized

velvet steppe
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well it won't compile if you don't initialize it, but you can initialize it

ancient python
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lol ok

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never saw this in other code tho

velvet steppe
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that doesn't mean it's not legal

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and that has nothing to do with references pointing to "temporary" objects

ancient python
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Ok my bad

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I probably missed it with rvalue

velvet steppe
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and one of the defining characteristics of pointers is that they don't always point to an object

ancient python
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yeah

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so thats why u use them as function argument instead of pointer to prevent ecxessive check on nullptr

velvet steppe
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well it depends

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if the argument might be null/missing then it's fine to use a pointer

ancient python
velvet steppe
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basically raw pointers should only be used as a nullable non-owning reference

velvet steppe
ancient python
velvet steppe
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because pointers can be null

ancient python
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but you can make setter that checks that

velvet steppe
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you don't always use getter/setter

ancient python
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so basically you just do it for

struct A
{
  B& value;
};

A a;
B b;
a.value = b;
velvet steppe
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there's basically no difference between struct and class in C++

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except the default access specifier

velvet steppe
ancient python
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well if I do it through constructor

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Because I thought that & can be used only within function

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And it wont work futher (like you should use perfect forwarding)

velvet steppe
ancient python
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like

A func1(B& b)
{
  return blablabla(b); 
}

A func2(B& b)
{
   return func1(b);
}
...
B& b;
A a = func2(b);
velvet steppe
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you can use them as function arguments and you can use them in other places

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just like other types

ancient python
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because it needs a B b paremeter

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no?

velvet steppe
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why not?

ancient python
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Maybe I remember it wrong

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But when I tried that it didnt work

velvet steppe
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you're thinking of r-value references, &&

ancient python
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Maybe

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That has to do something with perfect forwarding

velvet steppe
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perfect forwarding is when you take a templated argument and you don't know if it's an l-value or r-value and you want to forward it with the same type to another function

ancient python
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Yes

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So I was thinking that without perfect forwarding you are unable to pass & further

velvet steppe
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so basically it has nothing to do with what we discussed so far

ancient python
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Okay

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Thanks for explaining

velvet steppe
velvet steppe
ancient python
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Maybe

eternal peak
eternal peak
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or else your code ends up looking like python functions which have 20 parameters each 🤢

velvet steppe
eternal peak
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that doesn't happen when you pass in a temporary to a function, right?

velvet steppe
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yeah true

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actually technically it does I think