C++ implements the basic functions of the String class

　　This article only implements the constructor, destructor, assignment constructor and assignment function of the String class. Other operations will not be described in detail. The general written test interview will basically only require the realization of the functions of these four functions.

#include <iostream>
using namespace std;

class String {
 public :
     //     Constructor 
    String( const  char *str= NULL);
     //     Copy constructor 
    String( const String& other);
     //     Assignment function 
    String& operator =( const String & other);
     //     Destructor 
    ~String( void );
    
private:
    char *data;
};

String::String(const char * str) {
    if (str == NULL)
    {
        data = new char[1];
        *data = '\0';
    }
    else {
         int len ​​= strlen (str) + 1 ;
        data = new char[len];
        strcpy(data, str);
    }
    
}

String::String(const String& other) {
    int len = strlen(other.data) + 1;
    data = new char[len];
    strcpy(data, other.data);
}

String & String:: operator =( const String& other) {
     //     Determine whether it is self-assignment 
    if ( this == & other) 
         return * this ;

    delete[]data;

    int len = strlen(other) + 1;
    data = new char[len];
    strcpy(data, other.data);

    //     Return a reference to this object 
    return * this ;
}

String::~String() {
    delete[]data;
}