a. string& assign ( const string& str );

将str替换原字串的内容

举例：

string testassign = "Hello World";

testassign.assign("Go home");

cout<<testassign<<endl;

//打印结果为 go home

 

b. string& assign ( const string& str, size_t pos, size_t n );

将str的内容从位置pos起的n个字符作为原字串的新内容赋给原字串

string testassign = "Hello World";

testassign.assign("Come on!", 5, 2);

cout<<testassign<<endl;

//打印结果为 on

 

c. string& assign ( const char* s, size_t n );

将字符数组或者字符串的首n个字符替换原字符串内容

举例：

string testassign = "Hello World";

testassign.assign("go back to China", 7);

cout<<testassign<<endl;

//打印结果为go back

 

d. string& assign ( const char* s );

将字符串或者字符数组作为新内容替换原字串

举例：

string testassign = "Hello World";

char ch[20] = "go back to shanghai";

testassign.assign(ch);

cout<<testassign<<endl;

//打印结果为 go back to shanghai

 

e. string& assign ( size_t n, char c );

将原字串替换为n个字符c

举例：

string testassign = "Hello World";

char ch = ‘?‘;

testassign.assign(5, ch);

cout<<testassign<<endl;

//打印结果为?????

 

f. template <class InputIterator>   string& assign ( InputIterator first, InputIterator last );

需要include <iterator>

举例：

string testassign = "Hello World";

testassign.assign(istream_iterator<char>(cin), istream_iterator<char>());

//输入abcde

cout<<testassign<<endl;

//打印结果为 abcde

string substr(size_type _Off = 0,size_type _Count = npos) const;

string str("helloworld");
string strSub = str.substr(0, 5);