實戰c++中的string系列--string的串連(+= or append or push_back)

標籤：

string的串連也是經常用到的，string重載了一些運算子：
首先看一看重載+運算子，用於串聯兩個字串對象：
源碼：

template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator> operator+(      const basic_string<CharType, Traits, Allocator>& _Left,      const basic_string<CharType, Traits, Allocator>& _Right   );template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator> operator+(      const basic_string<CharType, Traits, Allocator>& _Left,      const CharType* _Right   );template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator> operator+(      const basic_string<CharType, Traits, Allocator>& _Left,      const CharType _Right   );template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator> operator+(      const CharType* _Left,      const basic_string<CharType, Traits, Allocator>& _Right   );template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator> operator+(      const CharType _Left,      const basic_string<CharType, Traits, Allocator>& _Right   );template<class CharType, class Traits, class Allocator>    basic_string<CharType, Traits, Allocator>&& operator+(        const basic_string<CharType, Traits, Allocator>& _Left,        const basic_string<CharType, Traits, Allocator>&& _Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      const basic_string<CharType, Traits, Allocator>&& _Left,      const basic_string<CharType, Traits, Allocator>& _Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      const basic_string<CharType, Traits, Allocator>&& _Left,      const basic_string<CharType, Traits, Allocator>&& _Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      const basic_string<CharType, Traits, Allocator>&& _Left,      const CharType *_Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      const basic_string<CharType, Traits, Allocator>&& _Left,      CharType _Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      const CharType *_Left,      const basic_string<CharType, Traits, Allocator>&& _Right);template<class CharType, class Traits, class Allocator>   basic_string<CharType, Traits, Allocator>&& operator+(      CharType _Left,      const basic_string<CharType, Traits, Allocator>&& _Rig

所以使用時，注意事項：

#include<iostream>#include<string>int main(){    std::string my_str = "holiday";    std::string my_str_add = "error" + "error";//錯誤    std::string my_str_add2 = my_str + "right";    std::string my_str_add3 = my_str + "right" + "right";    std::string my_str_add4 = "right" + my_str;    std::string my_str_add5 = "error" + "error" + my_str;//錯誤    return 0;}

下面開始正題!
+=
*將字元追加到字串*

basic_string<CharType, Traits, Allocator>& operator+=(   value_type _Ch);basic_string<CharType, Traits, Allocator>& operator+=(   const value_type* _Ptr);basic_string<CharType, Traits, Allocator>& operator+=(   const basic_string<CharType, Traits, Allocator>& _Right);

append
*添加字元為字串的末尾*

basic_string<CharType, Traits, Allocator>& append(    const value_type* _Ptr);basic_string<CharType, Traits, Allocator>& append(    const value_type* _Ptr,    size_type _Count);basic_string<CharType, Traits, Allocator>& append(    const basic_string<CharType, Traits, Allocator>& _Str,    size_type _Off,    size_type _Count);basic_string<CharType, Traits, Allocator>& append(    const basic_string<CharType, Traits, Allocator>& _Str);basic_string<CharType, Traits, Allocator>& append(    size_type _Count,     value_type _Ch);template<class InputIterator>    basic_string<CharType, Traits, Allocator>& append(        InputIterator _First,         InputIterator _Last    );basic_string<CharType, Traits, Allocator>& append(    const_pointer _First,    const_pointer _Last);basic_string<CharType, Traits, Allocator>& append(    const_iterator _First,    const_iterator _Last);

有多個重載函數，因此多種使用方法：

   string str1a ( "Hello " );   const char *cstr1a = "Out There ";   str1a.append ( cstr1a );   string str1b ( "Hello " );   const char *cstr1b = "Out There ";   str1b.append ( cstr1b , 3 );   string str1c ( "Hello " ), str2c ( "Wide World " );      str1c.append ( str2c , 5 , 5 );   string str1d ( "Hello " ), str2d ( "Wide " ), str3d ( "World " );   str1d.append ( str2d );   str1d += str3d;   string str1e ( "Hello " );   str1e.append ( 4 , ‘!‘ );   string str1f ( "Hello " ), str2f ( "Wide World " );   str1f.append ( str2f.begin ( ) + 5 , str2f.end ( ) - 1 );

push_back
*將元素添加到該字串的末尾*

void push_back(    value_type _Ch);

這裡需要注意的是，以下代碼是錯誤的：

my_str.push_back("123");//錯誤my_str.push_back(‘1‘);//ok

實戰c++中的string系列--string的串連(+= or append or push_back)