update

learn_class/modern_C++_30/RAII/RAII.cpp

@@ -0,0 +1,96 @@
+#include <iostream>
+#include <mutex>
+#include <fstream>
+using namespace std;
+
+enum class shape_type {
+    circle,
+    triangle,
+    rectangle,
+};
+
+
+class shape {
+public:
+    shape() { cout << "shape" << endl; }
+
+    virtual void print() {
+        cout << "I am shape" << endl;
+    }
+
+    virtual ~shape() {}
+};
+
+class circle : public shape {
+public:
+    circle() { cout << "circle" << endl; }
+
+    void print() {
+        cout << "I am circle" << endl;
+    }
+};
+
+class triangle : public shape {
+public:
+    triangle() { cout << "triangle" << endl; }
+
+    void print() {
+        cout << "I am triangle" << endl;
+    }
+};
+
+class rectangle : public shape {
+public:
+    rectangle() { cout << "rectangle" << endl; }
+
+    void print() {
+        cout << "I am rectangle" << endl;
+    }
+};
+
+// 利用多态 上转 如果返回值为shape,会存在对象切片问题。
+shape *create_shape(shape_type type) {
+    switch (type) {
+        case shape_type::circle:
+            return new circle();
+        case shape_type::triangle:
+            return new triangle();
+        case shape_type::rectangle:
+            return new rectangle();
+    }
+}
+
+class shape_wrapper {
+public:
+    explicit shape_wrapper(shape *ptr = nullptr) : ptr_(ptr) {}
+
+    ~shape_wrapper() {
+        delete ptr_;
+    }
+
+    shape *get() const {
+        return ptr_;
+    }
+
+private:
+    shape *ptr_;
+};
+
+
+void foo() {
+    shape_wrapper ptr(create_shape(shape_type::circle));
+    ptr.get()->print();
+}
+
+int main() {
+
+    // 第一种方式
+    shape *sp = create_shape(shape_type::circle);
+    sp->print();
+    delete sp;
+
+    // 第二种方式
+    foo();
+
+    return 0;
+}

learn_class/modern_C++_30/RAII/heap.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+
+using namespace std;
+
+class bar {
+
+};
+
+// java 程序员风格
+void foo() {
+    cout << "method 1" << endl;
+    bar *ptr = new bar();
+    delete ptr;
+}
+
+bar *make_bar() {
+    bar *ptr = nullptr;
+    try {
+        ptr = new bar();
+    } catch (...) {
+        delete ptr;
+        throw;
+    }
+    return ptr;
+}
+// 独立出函数  分配和释放不在一个函数里
+void foo1() {
+    cout << "method 2" << endl;
+    bar *ptr = make_bar();
+    delete ptr;
+}
+
+
+int main() {
+    foo();
+    foo1();
+    return 0;
+}

learn_class/modern_C++_30/RAII/stack.cpp

@@ -0,0 +1,26 @@
+//
+// Created by light on 19-12-9.
+//
+#include <iostream>
+class Obj {
+public:
+    Obj() { puts("Obj()"); }
+    ~Obj() { puts("~Obj()"); }
+};
+void foo(int n)
+{
+    Obj obj;
+    if (n == 42)
+        throw "life, the universe and everything";
+}
+// 不管是否发生了异常，obj 的析构函数都会得到执行。
+int main()
+{
+    try {
+        foo(41);
+        foo(42);
+    }
+    catch (const char* s) {
+        puts(s);
+    }
+}