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As you can see, I'm trying to let the computer know that the notepad class has a function retrieveButtons, and that the function will return a vector of type sf::Text.Code:vector<sf::Text> notepad::retrieveButtons(){
}
Is this possible? Or will I have to use pointers?
From what I have read you can return a vector no problem, but the larger the vector the more inefficient it becomes. There is also the possibility of just passing a vector to the function by reference. If I am recalling an article I read recently if you pass by reference you will only have one vector in memory, but if you return a vector from the function back to the original vector that you will use outside the function you are possibly doubling the memory usage for the same function.
There is a long discussion on the subject here as well.
how to return std::vector from function? - C / C++
This is typically not necessary.
The compiler can perform NRVO, thus preventing any copy at all.
Even if the compiler did have to do a copy, the move constructor will kick in, and the copy will typically be very cheap - two move operations. So don't worry about this. Return it as normal.
Thanks for that. I was not aware of this probably because I used an outdated compiler for quite to long. If the function accepted a vector class parameter would it still create a copy in memory for that case? Or are there optimization features for this as well?Quote:
The compiler can perform NRVO, thus preventing any copy at all.
If you take a reference, then obviously no copy of the vector itself will be made (granted that you work with the vector gotten as a reference, and not a temporary copy).
How would I return it normally is my main question. :confused:Quote:
Originally Posted by Elysia
As you can see, I'm not too sure how to return the buttons vector (declared in the class as: vector<sf::Text> buttons;); as a void I can't return anything, and I can't set the return type to vector or vector<sf::Text>.Code:void notepad::retrieveButtons(){
return &buttons;
}
Any hints?
Well, it would be something like
if buttons is a member variable, orCode:const std::vector<sf::Text>& notepad::RetrieveButtons()
{
return buttons;
}
if your buttons is a local variable.Code:std::vector<sf::Text> notepad::RetrieveButtons()
{
sf::Text blah(...); // Initialize and do stuff with blah
return blah;
}
If this doesn't work, then what is the error?
It is possible that the object type (sf::Text) cannot be copied (and not moved), and if that is the case, the later may not work.
The first code you provided worked fine without any errors.Quote:
Originally Posted by Elysia
However, may I ask why you moved the address symbol (&)? (from the return statement to the function type information)
Thanks.
It's a reference. It's not the address symbol anymore.Quote:
Originally Posted by Justin H
It's used to indicate that the return type is a reference. The code is returning a constant reference to the Text vector, instread of a copy. It can be used just like a copy, but it more efficent in case. It's not a pointer type, so you don't need to use the & operator to create it.Quote:
Originally Posted by Justin H
Reference types are also useful for passing parameters to functions.
Aha, thanks. This is a nice little feature. ;)
However, does this act just like a pointer? It's just not technically labeled as one?..
It acts as a pointer in that if the data refered by a refence is be changed, and this change can be seen using the reference, and non-const references can make changes to the original.
However, syntatically, it is used just like a copy.
Ah, makes complete sense.Quote:
Originally Posted by King Mir
Thanks. :)