Common String Methods

Append

We saw that adding new characters to the end of a string using indexing is not possible. However, there is a convenient .append() method for this purpose.

append.h

str.append("added part");


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str.append("added part");

Concatenate

Another way to do it is by using the + operator. It performs concatenation when applied to strings.

main.cpp

#include <iostream>

int main()

{

std::string str = "Code";

str = str + "finity"; // or str += "finity"

std::cout << str << std::endl;

}


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#include <iostream>

int main()
{
    std::string str = "Code";
    str = str + "finity"; // or str += "finity"
    std::cout << str << std::endl;
}

It also allows adding text to the beginning or to both ends, which .append() is incapable of.

main.cpp

#include <iostream>

int main()

{

std::string str = "finity";

str = "code" + str + ".com";

std::cout << str << std::endl;

}


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#include <iostream>

int main()
{
    std::string str = "finity";
    str = "code" + str + ".com";
    std::cout << str << std::endl;
}

Insert

You can insert new text into a string at a specific position using the .insert() method.

insert.h

str.insert(pos, "text to add");


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str.insert(pos, "text to add");

The position, specified by the pos parameter, determines where the new text will be added.

The new text is inserted before the character currently at the given position. This method is useful for dynamically modifying strings without creating new ones.

Replace

You can also replace a part of a string with a different string. This is achievable using the .replace() method.

replace.h

str.replace(start, n, "new text");


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str.replace(start, n, "new text");

Here start means the index of the first element to replace, and n stands for the length of a part to replace.

The following is a gif of how .replace() works.

Erase

You can also remove a portion of a string using the .erase() method. This is useful when you need to delete specific characters or substrings from a string.

erase.h

str.erase(start, n);


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str.erase(start, n);

If the n parameter matches or exceeds the remaining length of the string from start, all characters from start onward will be erased.

The start and n parameters work similarly to those in the .replace() method, providing flexibility to modify the string as needed.

main.cpp

#include <iostream>

int main()

{

std::string str = "finity";

str.append(".com"); // finity to finity.com

std::cout << str << std::endl;

str = "in" + str; // finity.com to infinity.com

std::cout << str << std::endl;

str.insert(2, "de"); // infinity.com to indefinity.com

std::cout << str << std::endl;

str.replace(0, 2, "co"); // indefinity.com to codefinity.com

std::cout << str << std::endl;

str.erase(10, 4); // codefinity.com to codefinity

std::cout << str << std::endl;

}


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#include <iostream>

int main()
{
    std::string str = "finity";
    
    str.append(".com"); // finity to finity.com
    std::cout << str << std::endl;
    
    str = "in" + str; // finity.com to infinity.com
    std::cout << str << std::endl;
    
    str.insert(2, "de"); // infinity.com to indefinity.com
    std::cout << str << std::endl;
    
    str.replace(0, 2, "co"); // indefinity.com to codefinity.com
    std::cout << str << std::endl;
    
    str.erase(10, 4); // codefinity.com to codefinity
    std::cout << str << std::endl;
}

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Sezione 3. Capitolo 4

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