1 #include <vector>
  2 #include <cassert>
  3 #include <string>
  4 #include <iostream>
  5 using namespace std;
  6 
  7 class String
  8 {
  9 public:
 10     String();
 11     String(int n, char c);
 12     String(const char* source);
 13     String(const String& s);
 14     String(String&& s);
 15     String& operator=(char* s);
 16     String& operator=(const String& s);
 17     String& operator=(String&& s);
 18     ~String();
 19 
 20     char& operator[](int i);
 21     const char& operator[](int i) const;
 22     String& operator+=(const String& s);
 23     String& operator+=(const char* s);
 24 
 25     friend ostream& operator<<(ostream& out, String& s);
 26     friend ostream& operator<<(ostream& out, const String& s);
 27     friend istream& operator>>(istream& in, String& s);
 28 
 29     friend bool operator<(const String& left, const String& right);
 30     friend bool operator>(const String& left, const String& right);
 31     friend bool operator==(const String& left, const String& right);
 32     friend bool operator!=(const String& left, const String& right);
 33 
 34     int getSize() const;
 35     void setSize(int nSize);
 36     char* getData() const;
 37     void setData(char* pData);
 38 
 39 private:
 40     void init();
 41 
 42 private:
 43     int m_size;
 44     char* m_data;
 45 };
 46 
 47 void String::init()
 48 {
 49     m_data = new char[1];
 50     assert(m_data != NULL);
 51     *m_data = ‘\0‘;
 52     m_size = 0;
 53 }
 54 
 55 String::String()
 56 {
 57     cout << "call String()" << endl;
 58     init();
 59 }
 60 
 61 String::String(int n, char c)
 62 {
 63     cout << "call String(int n, char c)" << endl;
 64     m_data = new char[n + 1];
 65     assert(m_data != NULL);
 66     m_size = n;
 67     char* temp = m_data;
 68     while (n--)
 69     {
 70         *temp++ = c;
 71     }
 72     *temp = ‘\0‘;
 73 }
 74 
 75 String::String(const char* source)
 76 {
 77     cout << "call String(const char* source)" << endl;
 78     if (NULL == source)
 79     {
 80         init();
 81     }
 82     else
 83     {
 84         m_size = strlen(source);
 85         m_data = new char[m_size + 1];
 86         assert(m_data != NULL);
 87         strcpy_s(m_data, (m_size + 1), source);
 88     }
 89 }
 90 String::String(const String& s)
 91 {
 92     cout << "call String(const String& s)" << endl;
 93     m_data = new char[s.m_size + 1];
 94     assert(m_data != NULL);
 95     strcpy_s(m_data, (s.m_size + 1), s.m_data);
 96     m_size = s.m_size;
 97 }
 98 
 99 String::String(String&& s)
100 {
101     cout << "call move ctor" << endl;
102     m_data = s.getData();
103     m_size = s.getSize();
104     s.setData(NULL);
105     s.setSize(0);
106 }
107 
108 String& String::operator=(char* s)
109 {
110     cout << "call operator=(char* s)" << endl;
111 
112     if (m_data != NULL)
113     {
114         delete []m_data;
115     }
116     m_size = strlen(s);
117     m_data = new char[m_size + 1];
118     assert(m_data != NULL);
119     strcpy_s(m_data, (m_size + 1), s);
120     return (*this);
121 }
122 
123 String& String::operator=(const String& s)
124 {
125     cout << "call operator=(const String& s)" << endl;
126 
127     if (this == &s)
128     {
129         return *this;
130     }
131     if (m_data != NULL)
132     {
133         delete []m_data;
134     }
135     m_size = strlen(s.m_data);
136     m_data = new char[m_size + 1];
137     assert(m_data != NULL);
138     strcpy_s(m_data, (m_size + 1), s.m_data);
139     return (*this);
140 }
141 
142 String& String::operator=(String&& s)
143 {
144     cout << "call move operator=" << endl;
145 
146     if (this == &s)
147     {
148         return (*this);
149     }
150     if (m_data != NULL)
151     {
152         delete[]m_data;
153     }
154     m_data = s.getData();
155     m_size = s.getSize();
156     s.setData(NULL);
157     s.setSize(0);
158     return (*this);
159 }
160 
161 String::~String()
162 {
163     if (m_data != NULL)
164     {
165         delete[]m_data;
166         m_data = NULL;
167         m_size = 0;
168     }
169 }
170 
171 char& String::operator[](int i)
172 {
173     return m_data[i];
174 }
175 
176 const char& String::operator[](int i) const
177 {
178     return m_data[i];
179 }
180 
181 String& String::operator+=(const String& s)
182 {
183     int len = m_size + s.m_size + 1;
184     char* pTemp = m_data;
185     m_data = new char[len];
186     assert(m_data != NULL);
187     strcpy_s(m_data, (m_size + 1), pTemp);
188     strcat_s(m_data, len, s.m_data);
189     m_size = len - 1;
190     delete[]pTemp;
191     return (*this);
192 }
193 
194 String& String::operator+=(const char* s)
195 {
196     if (NULL == s)
197     {
198         return (*this);
199     }
200     int len = m_size + strlen(s) + 1;
201     char* pTemp = m_data;
202     m_data = new char[len];
203     assert(m_data != NULL);
204     strcpy_s(m_data, (m_size + 1), pTemp);
205     strcat_s(m_data, len, s);
206     m_size = len - 1;
207     delete[]pTemp;
208     return (*this);
209 }
210 
211 int String::getSize() const
212 {
213     return m_size;
214 }
215 
216 void String::setSize(int nSize)
217 {
218     this->m_size = nSize;
219 }
220 
221 char* String::getData() const
222 {
223     return m_data;
224 }
225 
226 void String::setData(char* pData)
227 {
228     if (NULL == pData)
229     {
230         init();
231     }
232     else
233     {
234         m_data = pData;
235     }
236 }
237 
238 ostream& operator<<(ostream& out, String& s)
239 {
240     for (int i = 0; i < s.getSize(); ++i)
241     {
242         out << s[i] << " ";
243     }
244     return out;
245 }
246 
247 ostream& operator<<(ostream& out, const String& s)
248 {
249     for (int i = 0; i < s.getSize(); ++i)
250     {
251         out << s[i] << " ";
252     }
253     return out;
254 }
255 
256 istream& operator>>(istream& in, String& s)
257 {
258     char p[50];
259     in.getline(p, 50);
260     s = p;
261     return in;
262 }
263 
264 bool operator<(const String& left, const String& right)
265 {
266     int i = 0;
267     while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
268         i++;
269 
270     return (left[i] - right[i] < 0);
271 }
272 
273 bool operator>(const String& left, const String& right)
274 {
275     int i = 0;
276     while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
277         i++;
278 
279     return (left[i] - right[i] > 0);
280 }
281 
282 bool operator==(const String& left, const String& right)
283 {
284     int i = 0;
285     while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
286         i++;
287 
288     return (left[i] == right[i]);
289 }
290 
291 bool operator!=(const String& left, const String& right)
292 {
293     int i = 0;
294     while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
295         i++;
296 
297     return (left[i] != right[i]);
298 }
299 
300 int main()
301 {
302     std::vector<String> stringVector;
303 
304     String str(3, ‘a‘);
305     String str1(str);
306     String str2("asdf");
307     String str3 = str2;
308 
309     cout << "str: " << str << endl;
310     cout << "str1: " << str1 << endl;
311     cout << "str2: " << str2 << endl;
312     cout << "str3: " << str3 << endl;
313 
314     stringVector.push_back(str);
315     stringVector.push_back(str1);
316     stringVector.push_back(str2);
317     stringVector.push_back(str3);
318 
319     // 第一种方式
320     cout << "the first way: " << endl;
321     for (auto item : stringVector)
322     {
323         cout << item << endl;
324     }
325 
326     // 第二种方式：引用，可以修改元素值
327     cout << "the second way: " << endl;
328     for (auto& item : stringVector)
329     {
330         item += "baidu";
331         cout << item << endl;
332     }
333 
334     // 第三种方式
335     cout << "the third way: " << endl;
336     for (auto & const item : stringVector)
337     {
338         cout << item << endl;
339     }
340 
341     // 第四种方式
342     cout << "the four way: " << endl;
343     for (auto const & item : stringVector)
344     {
345         cout << item << endl;
346     }
347 
348     // 第五种方式：万能引用 
349     //参考：https://isocpp.org/blog/2012/11/universal-references-in-c11-scott-meyers
350     cout << "the five way: " << endl;
351     for (auto&& item : stringVector)
352         cout << item << endl;
353 
354     // 第六种方式
355     cout << "the six way: " << endl;
356     for (auto& item : { "abc", "def", "hij" })
357         cout << item << endl;
358 
359     // 第七种方式
360     cout << "the seven way: " << endl;
361     for (auto& item : { 100, 200, 300 })
362         cout << item << endl;
363 
364 #if 0
365     // 第七种方式：编译错误
366     cout << "the seven way: " << endl;
367     for (int& item : { 100, 200, 300 })
368         cout << item << endl;
369 #endif
370 
371     system("pause");
372 }