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String Assignment | C++ STL

String Assignment in C++ STL (Standard Template Library): In this article, we are going to learn how to assign a string in C++ STL and how to concatenate the strings?
Submitted by IncludeHelp, on August 19, 2018

C++ STL - string Class

In C++ STL, with "string" class, we can assign, replace string by using assignment operator (=), there is no more need to using strcpy() to assign the string after the declaration.

How to assign/replace the string?

Use assignment operator (=)

Syntax

string_object = "string_value"

Note: we can also assign a single character to the string.

Here is an example with sample input and output:

//declaration
string str;

//assignment
str = "Hello world!"

Example

#include <iostream>
#include <string>

using namespace std;

int main() {
  // declare string object
  string str;

  // assign string
  str = "Hello World!";

  // print string
  cout << "str: " << str << endl;

  // replace i.e. re-assign string again
  str = "How are you?";

  // print string
  cout << "str: " << str << endl;

  // assign single character
  str = 'H';
  cout << "str: " << str << endl;

  return 0;
}

Output

str: Hello World!
str: How are you?
str: H

Concatenate string and assignment

Yes, we can concatenate two strings by using plus (+) operator and assign it to the string.

Here is an example with sample input and output:

Input:
str1: Hello world,
str2: How are you?

Concatenation:
str3 = str1+ str2

Output:
str3: Hello world, How are you?

Example

#include <iostream>
#include <string>

using namespace std;

int main() {
  // declare string objects
  string str1, str2, str3;

  // assign the strings
  str1 = "Hello world";
  str2 = "How are you?";

  // concatenate str1, str2 along with space and assign to str3
  str3 = str1 + ' ' + str2;

  // print the string values
  cout << "str1: " << str1 << endl;
  cout << "str2: " << str2 << endl;
  cout << "str3: " << str3 << endl;

  return 0;
}

Output

str1: Hello world
str2: How are you?
str3: Hello world How are you?