C++ std::string::append()用法及代码示例

该成员函数在字符串的末尾附加字符。

1. 语法1：附加字符串str的字符。如果结果大小超过最大字符数，它将抛出length_error。

   string& string::append (const string& str)
   
   str: is the string to be appended.
   返回： *this

   // CPP code to demonstrate append(str) 
      
   #include <iostream> 
   #include <string> 
   using namespace std; 
      
   // Function to demonstrate append() 
   void appendDemo(string str1, string str2) 
   { 
       // Appends str2 in str1 
       str1.append(str2); 
       cout << "Using append():"; 
       cout << str1 << endl; 
   } 
      
   // Driver code 
   int main() 
   { 
       string str1("Hello World! "); 
       string str2("GeeksforGeeks"); 
      
       cout << "Original String:" << str1 << endl; 
       appendDemo(str1, str2); 
      
       return 0; 
   }

   输出：

   
   

   Original String:Hello World! 
   Using append():Hello World! GeeksforGeeks
   

2. 语法2：最多附加字符串str的str_num字符，从索引str_idx开始。如果str_idx> str，则抛出out_of_range。 size()。如果结果大小超过最大字符数，它将抛出length_error。

   string& string::append (const string& str, size_type str_idx, size_type str_num)
   
   str: is the string to be appended
   str_num: being number of characters
   str_idx: is index number.
   返回：*this.
   

   // CPP code to demonstrate  
   // append(const char* chars, size_type chars_len) 
     
   #include <iostream> 
   #include <string> 
   using namespace std; 
      
   // Function to demonstrate append() 
   void appendDemo(string str1, string str2) 
   { 
       // Appends 5 characters from 0th index of 
       // str2 to str1 
       str1.append(str2, 0, 5); 
       cout << "Using append():"; 
       cout << str1; 
   } 
      
   // Driver code 
   int main() 
   { 
       string str1("GeeksforGeeks "); 
       string str2("Hello World! "); 
      
       cout << "Original String:" << str1 << endl; 
       appendDemo(str1, str2); 
      
       return 0; 
   }

   输出：

   Original String:GeeksforGeeks 
   Using append():GeeksforGeeks Hello
   

3. 语法3：追加C-string cstr的字符。如果结果大小超过最大字符数，则抛出length_error。

   string& string::append (const char* cstr)
   
   *cstr: is the pointer to C-string.
   Note: that cstr may not be a null pointer (NULL).
   返回： *this
   

   // CPP code to demonstrate append(const char* cstr) 
     
   #include <iostream> 
   #include <string> 
   using namespace std; 
      
   // Function to demonstrate append 
   void appendDemo(string str) 
   { 
       // Appends "GeeksforGeeks" 
       // in str 
       str.append("GeeksforGeeks"); 
       cout << "Using append():"; 
       cout << str << endl; 
   } 
      
   // Driver code 
   int main() 
   { 
       string str("World of "); 
      
       cout << "Original String:" << str << endl; 
       appendDemo(str); 
      
       return 0; 
   }

   输出：

   Original String:World of 
   Using append():World of GeeksforGeeks
   

4. 语法4：追加字符数组chars的chars_len字符。如果结果大小超过最大字符数，则抛出length_error。

   string& string::append (const char* chars, size_type chars_len)
   
   *chars is the pointer to character array to be appended.
   chrs_len: is the number of characters from *chars to be appended.
   Note that chars must have at least chars_len characters. 
   返回： *this.
   

   // CPP code to demonstrate  
   // (const char* chars, size_type chars_len) 
     
   #include <iostream> 
   #include <string> 
   using namespace std; 
      
   // Function to demonstrate append 
   void appendDemo(string str) 
   { 
       // Appends 5 characters from "GeeksforGeeks" 
       // to str 
       str.append("GeeksforGeeks", 5); 
       cout << "Using append():"; 
       cout << str << endl; 
   } 
      
   // Driver code 
   int main() 
   { 
       string str("World of "); 
      
       cout << "Original String:" << str << endl; 
       appendDemo(str); 
      
       return 0; 
   }

   输出：

   Original String:World of 
   Using append():World of Geeks
   

5. 语法5：追加字符c的出现次数。如果结果大小超过最大字符数，则抛出length_error。

   string& string::append (size_type num, char c)
   
   num: is the number of occurrences
   c:is the character which is to be appended repeatedly. 
   返回： *this.
   

   // CPP code to illustrate 
   // string& string::append (size_type num, char c) 
       
   #include <iostream> 
   #include <string> 
   using namespace std; 
       
   // Function to demonstrate append 
   void appendDemo(string str) 
   { 
       // Appends 10 occurrences of '$' 
       // to str 
       str.append(10, '$'); 
       cout << "After append():"; 
       cout << str; 
      
   } 
              
   // Driver code 
   int main() 
   { 
       string str("#########"); 
      
       cout << "Original String:" << str << endl; 
       appendDemo(str); 
       
       return 0; 
   }

   输出：

   Original String:#########
   After append():#########$$$$$$$$$$
   

6. 语法6：追加范围[beg，end)的所有字符。如果结果大小超过最大字符数，则抛出length_error。

   string& string::append (InputIterator beg, InputIterator end)
   
   first, last:Input iterators to the initial and final positions 
   in a sequence.
   返回 *this.
   

   // CPP code  to illustrate 
   // append (InputIterator beg, InputIterator end) 
      
   #include <iostream> 
   #include <string> 
   using namespace std; 
      
   // Function to demonstrate append 
   void appendDemo(string str1, string str2) 
   { 
      
       // Appends all characters from 
       // str2.begin()+5, str2.end() to str1 
       str1.append(str2.begin() + 5, str2.end()); 
       cout << "Using append:"; 
       cout << str1; 
   } 
   // Driver code 
   int main() 
   { 
       string str1("Hello World! "); 
       string str2("GeeksforGeeks"); 
      
       cout << "Original String:" << str1 << endl; 
       appendDemo(str1, str2); 
      
       return 0; 
   }

   输出：

   Original String:Hello World! 
   Using append:Hello World! forGeeks