静态数据成员

base/new/stringbad.cpp

@@ -0,0 +1,39 @@
+//
+// Created by nicemoe on 2021/8/18.
+//
+
+#include  <cstring>
+#include "StringBad.h"
+
+using std::cout;
+using std::endl;
+
+int StringBad::num_strings = 0;
+
+StringBad::StringBad(const char *s) {
+    len = std::strlen(s);
+    str = new char[len + 1];
+    std::strcpy(str, s);
+    num_strings++;
+    cout << num_strings << " : \"" << str << "\" object created" << endl;
+}
+
+StringBad::StringBad() {
+    len = 4;
+    str = new char[4];
+    std::strcpy(str, "C++");
+    num_strings++;
+    cout << num_strings << " : \"" << str << "\" object created" << endl;
+}
+
+StringBad::~StringBad() {
+    cout << "\"" << str << "\" object deleted" << endl;
+    --num_strings;
+    cout << num_strings << " left" << endl;
+    delete[] str;
+}
+
+std::ostream &operator<<(std::ostream &os, const StringBad &st) {
+    os << st.str;
+    return os;
+}

base/new/stringbad.h

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+//
+// Created by nicemoe on 2021/8/18.
+//
+
+#ifndef BASE_STRINGBAD_H
+#define BASE_STRINGBAD_H
+#include <iostream>
+
+class StringBad {
+
+private:
+    char * str;
+    int len;
+    static int num_strings;
+public:
+    StringBad(const char * s);
+    StringBad();
+    ~StringBad();
+    friend std::ostream & operator<<(std::ostream & os,const StringBad & st);
+};
+
+
+#endif //BASE_STRINGBAD_H

base/new/vegnews.cpp

@@ -0,0 +1,49 @@
+//
+// Created by nicemoe on 2021/8/18.
+//
+
+#include  <iostream>
+#include "stringbad.h"
+
+using std::cout;
+using std::endl;
+
+void callme1(StringBad &);
+
+void callme2(StringBad);
+
+int main() {
+    {
+        cout << "Starting an inner block." << endl;
+        StringBad headline1("Celery Stalk at Midnght");
+        StringBad headline2("Lettuce Prey");
+        StringBad sports("Spinach Leaves Bowl for Dollars");
+        cout << "headline1: " << headline1 << endl;
+        cout << "headline2: " << headline2 << endl;
+        cout << "sports: " << sports << endl;
+        callme1(headline1);
+        cout << "headline1: " << headline1 << endl;
+        callme2(headline2);
+        cout << "headline2: " << headline2 << endl;
+        cout << "Initialize one object to another:" << endl;
+        StringBad sailor = sports;
+        cout << "sailor: " << sailor << endl;
+        cout << "Assign one object to another:\n";
+        StringBad knot;
+        knot = headline1;
+        cout << "knot: " << knot << endl;
+        cout << "Exiting the block." << endl;
+    }
+    cout << "End of main()" << endl;
+    return 0;
+}
+
+void callme1(StringBad &rsb) {
+    cout << "String passed by reference:" << endl;
+    cout << "  \"" << rsb << " \"" << endl;
+}
+
+void callme2(StringBad sb) {
+    cout << "String passed by value:" << endl;
+    cout << "  \"" << sb << " \"" << endl;
+}