cpp -- Object-Oriented Thinking(1)

The string Class

A better way to create a string is to use the string constructor like this:

string s("Welcome to C++");

Append

• 接一个string

string s1("Welcome");
s1.append(" to C++"); // Appends " to C++" to s1
cout << s1 << endl; // s1 now becomes Welcome to C++

• 接一个string从index开始的n个字符

string s2("Welcome");
s2.append(" to C and C++", 0, 5); // Appends " to C" to s2
cout << s2 << endl; // s2 now becomes Welcome to C

• 接一个string的前n个字符

string s3("Welcome");
s3.append(" to C and C++", 5); // Appends " to C" to s3
cout << s3 << endl; // s3 now becomes Welcome to C

• 接n次这个string

string s4("Welcome");
s4.append(4, 'G'); // Appends "GGGG" to s4
cout << s4 << endl; // s4 now becomes WelcomeGGGG

Assign

跟上一个用法类似

at, clear, erase, and empty

at 可以用方括号代替

length, size, capacity, and c_str()

length(), size()是一样的。c_str() 和 data()是一样的

Substring

• substr(index: int, n: int) 从index开始的n个字符
• substr(index: int) 从index开始的后面所有

Searching in a String

用find函数搜索一个字符或者子串，如果找不到，返回的是string::npos

string s1("Welcome to HTML");
cout << s1.find("co") << endl; // Returns 3
cout << s1.find("co", 6) << endl; // Returns string::npos
cout << s1.find('o') << endl; // Returns 4
cout << s1.find('o', 6) << endl; // Returns 9

Inserting and Replacing Strings

• insert(index: int, s: string) 在index的位置插入字符s

string s1("Welcome to HTML");
s1.insert(11, "C++ and ");
cout << s1 << endl; // s1 becomes Welcome to C++ and HTML

• insert(index: int, n: int, ch: char) 在index插入n次字符ch

string s2("AA");
s2.insert(1, 4, 'B');
cout << s2 << endl; // s2 becomes to ABBBBA

• replace(index: int, n: int, s: string) 从index开始的n个字符，用s来替换

string s3("Welcome to HTML");
s3.replace(11, 4, "C++");
cout << s3 << endl; // s3 becomes Welcome to C++

String Operators

等于号其实是把一个string的内容copy到另一个string

string s1 = "ABC";

Instance and Static Members

A static variable is shared by all objects of the class. A static function cannot access instance members of the class.