vault backup: 2022-07-06 20:53:32

Affected files:
02. PARA/03. Resources（資源）/C++17/Structured binding declaration.md

02. PARA/03. Resources（資源）/C++17/Structured binding declaration.md

@@ -34,4 +34,24 @@ auto& [num1, num2, num3] = my_vec;
 ```cpp
 float rect[4]{ 5.0f, 6.0f, 120.0f, 200.0f };
 auto& [x, y, w, h] = rect;
-```
+```
+
+但是不能用來展開 `std::vector`。
+
+## 展開 pair
+```cpp
+std::pair<std::string, int32_t> name_phone{ "John", 912345678 };
+auto& [name, phone_number] = name_phone;
+```
+
+用在 for-loop 裡也比較好懂，假設我們有一個 vector 用來存剛剛的姓名跟電話：
+```cpp
+std::vector<std::pair<std::string, uint32_t>> phoneBook = {
+    { "John", 912345678 },
+    { "Andy", 912345679 },
+};
+
+for (const auto& [name, phone] : phoneBook) {
+    std::cout << "Name: " << name << ", phone: " << phone << std::endl;
+}
+```