Simple C++ String Class

Every C++ programmer knows that the standard library has a string class. But, while learning, it’s a good idea to know how to develop your own string class.

That’s why I made the String class. It’s not intended for professional projects (for them, you should use the standard library’s string), but as help to learn C++.

class String
{
	char *m_pszString;	//Allocated buffer
	int m_nAllocated;	//Allocated length

public:
	//Construction and destruction
	String() { /* ... */ }
	~String() { /* ... */ }

	//Copy constructors
	String(const char *pszString) { /* ... */ }
	String(const String& rsString) { /* ... */ }

	//Operators (assignment)
	String& operator=(const char *pszString);
	String& operator=(const String& rsString) { /* ... */ }

	//Operators (concatenation)
	String& operator+=(const char *pszString);
	String& operator+=(String& rsString) { /* ... */ }
	String operator+(String rsString);

	//Operators (comparison)
	bool operator<(String sString) { /* ... */ }
	bool operator<=(String sString) { /* ... */ }

	bool operator>(String sString) { /* ... */ }
	bool operator>=(String sString) { /* ... */ }

	bool operator==(String sString) { /* ... */ }
	bool operator!=(String sString) { /* ... */ }

	//Operations
	void Clear();
	String Lower() { /* ... */ }
	String Upper() { /* ... */ }

	//Information
	int Length() { /* ... */ }

	//Cast operators
	operator const char*() { /* ... */ }

protected:	//Helper functions
	/* ... */
};

//Output e input
std::ostream& operator<<(std::ostream& oStream, String& rsString);
std::istream& operator>>(std::istream& iStream, String& rsString);

This is a sample project made to explain the String class usage.

#include <iostream>
	using std::cout;
	using std::cin;
	using std::endl;
#include "String.h"

using namespace std;

int main(int argc, char *argv[])
{
	cout << "String sample project" << endl;
	cout << "---------------------" << endl << endl;

	String a("This"), b("is"), c("a"), d("test");
	String e = a + " " + b + " " + c + " " + d;

	cout << "String parts:" << endl;
	cout << '\t' << a << endl;
	cout << '\t' << b << endl;
	cout << '\t' << c << endl;
	cout << '\t' << d << endl << endl;

	cout << "Concatenated with spaces:" << endl;
	cout << '\t' << e << endl << endl;

	String f, g;

	cout << "Please input a string (empty to break): ";
	cin >> f;
	cout << "Please input other string (empty to break): ";
	cin >> g;

	cout << endl;

	cout << "1st string (" << f << ") is " << f.Length() << " chars long." << endl;
	cout << "2nd string (" << g << ") is " << g.Length() << " chars long." << endl;

	cout << endl;

	cout << "1st string in lowercase is " << f.Lower() << endl;
	cout << "1st string in uppercase is " << f.Upper() << endl << endl;

	cout << "2nd string in lowercase is " << g.Lower() << endl;
	cout << "2nd string in uppercase is " << g.Upper() << endl << endl;

	cout << "1 < 2\t=> " << (f<g?"true":"false") << endl;
	cout << "1 <= 2\t=> " << (f<=g?"true":"false") << endl;
	cout << "1 > 2\t=> " << (f>g?"true":"false") << endl;
	cout << "1 >= 2\t=> " << (f>=g?"true":"false") << endl;
	cout << "1 == 2\t=> " << (f==g?"true":"false") << endl;
	cout << "1 != 2\t=> " << (f!=g?"true":"false") << endl << endl;

	if (f == g)
		cout << "Strings are equal." << endl;
	else
		cout << "Strings are not equal." << endl;

	cout << endl;

	cout << "1+2\t=> " << f+g << endl;
	cout << "2+1\t=> " << g+f << endl;

	cout << endl;

    return 0;
}

And this is its output:

String sample project
---------------------

String parts:
        This
        is
        a
        test

Concatenated with spaces:
        This is a test

Please input a string (empty to break): Hello, string 1
Please input other string (empty to break): Phrase 2

1st string (Hello, string 1) is 15 chars long.
2nd string (Phrase 2) is 8 chars long.

1st string in lowercase is hello, string 1
1st string in uppercase is HELLO, STRING 1

2nd string in lowercase is phrase 2
2nd string in uppercase is PHRASE 2

1 < 2   => false
1 <= 2  => false
1 > 2   => true
1 >= 2  => true
1 == 2  => false
1 != 2  => true

Strings are not equal.

1+2     => Hello, string 1Phrase 2
2+1     => Phrase 2Hello, string 1

The code completely is portable.

It’s been developed, compiled and tested using wxDev-C++ for Windows with the MinGW compiler (included in the bundle).

String is licensed under the GNU GPL v3 (attached)…

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