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C++17 in Detail: A Deep Dive

Initializing string Members from string_view

Explore the techniques for initializing string members from std::string_view and compare passing std::string by value, reference, or move. Understand the implications of Small String Optimization on performance and learn when passing by value is preferred for safer and simpler code.

We'll cover the following...

Last time, we were left with this code:

C++ 17
#include <iostream>
#include <string>
#include <string_view>
using namespace std;
class UserName 
{ 
  std::string mName;
  public:
  UserName(std::string_view sv) : mName(sv) { }
  std::string_view getName(){return mName;}
};
std::string GetString() { return "some string..."; }
int main(){
  // creation from a string literal
  UserName u1{"John With Very Long Name"};
  cout << u1.getName() << endl;
  
  // creation from l-value:
  std::string s2 {"Marc With Very Long Name"};
  UserName u2 { s2 };
  cout << u2.getName() << endl;
  // use s2 later...
  
  // from r-value reference
  std::string s3 {"Marc With Very Long Name"};
  UserName u3 { std::move(s3) };
  cout << u3.getName() << endl;
  // third case is also similar to taking a return value: 
  
  UserName u4 { GetString() };
  cout << u4.getName() << endl;
}

Since the introduction of move semantics in ...

C++
class UserName { 
  std::string mName;
  public:
  UserName(std::string str) : mName(std::move(str)) { }
};

Now we have the following ...