returning a reference to string

Hi,

How do I properly put this to code? I am trying to return a string (name) from a function using reference.

Code:

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std::string& name()
{
  cout << "Enter your name: " << endl;
  getline(cin, name);
}

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I hope you get the idea. Thanks!

You need to pass in the string by reference, but you probably should either rename the function or use a different name for the string reference parameter. Of course, once you pass in the string by reference, there is not much point in returning it at all.

I think there are some cases that benefit from returning a reference. For example, I have a function to convert something to a string, and use the converted string in a string expression. I can pass in a string reference, store the converted string in it, and return a reference to it. This way, I can avoid a string copy operation. Here is some abstract code to explain what I mean:

Code:

---

string & int2str(int i, string & str){
  // convert i into str
  return str;
}

int main(){

  ...
  string tmp;
  string a = "abc" + int2str(20, tmp);
  ...
}

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Quote:

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Originally Posted by laserlight

You need to pass in the string by reference, but you probably should either rename the function or use a different name for the string reference parameter. Of course, once you pass in the string by reference, there is not much point in returning it at all.

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Quote:

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Originally Posted by plutino

I think there are some cases that benefit from returning a reference.

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Yes, but I do not think that this is one of them.

Quote:

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Originally Posted by plutino

This way, I can avoid a string copy operation.

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Depending on your point of view, you either cannot avoid the copy (since you are initialising a new string with a temporary) or can avoid the copy either way, e.g.,

Code:

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string tmp;
int2str(20, tmp);
string a = "abc" + tmp;

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The compiler can also optimize away functions returning copies of variables, if they are not too complicated.
But you cannot return a reference to a local variable!

You are right. I guess the only benefit (depending on your point of view) is to make the code more compact.

Quote:

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Originally Posted by laserlight

Yes, but I do not think that this is one of them.


Depending on your point of view, you either cannot avoid the copy (since you are initialising a new string with a temporary) or can avoid the copy either way, e.g.,

Code:

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string tmp;
int2str(20, tmp);
string a = "abc" + tmp;

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