book: translation of ch05

Update #12

code/5/5.2.unique.ptr.cpp

@@ -0,0 +1,50 @@
+//
+// 5.2.unique.ptr.cpp
+// chapter 05 start pointers and memory management
+// modern c++ tutorial
+//
+// created by changkun at changkun.de
+// https://github.com/changkun/modern-cpp-tutorial
+//
+
+#include <iostream>
+#include <memory>
+
+struct Foo {
+    Foo()      { std::cout << "Foo::Foo" << std::endl;  }
+    ~Foo()     { std::cout << "Foo::~Foo" << std::endl; }
+    void foo() { std::cout << "Foo::foo" << std::endl;  }
+};
+
+void f(const Foo &) {
+    std::cout << "f(const Foo&)" << std::endl;
+}
+
+int main() {
+    std::unique_ptr<Foo> p1(std::make_unique<Foo>());
+    
+    // p1 is not empty, prints
+    if (p1) p1->foo();
+    {
+        std::unique_ptr<Foo> p2(std::move(p1));
+        
+        // p2 is not empty, prints
+        f(*p2);
+        
+        // p2 is not empty, prints
+        if(p2) p2->foo();
+        
+        // p1 is empty, no prints
+        if(p1) p1->foo();
+        
+        p1 = std::move(p2);
+        
+        // p2 is empty, no prints
+        if(p2) p2->foo();
+        std::cout << "p2 was destroied" << std::endl;
+    }
+    // p1 is not empty, prints
+    if (p1) p1->foo();
+    
+    // Foo instance will be destroied when leaving the scope
+}