Awin Huang
b9da824cf9
Affected files: 02. PARA/03. Resources（資源）/C++17/Structured binding declaration.md
37 lines
861 B
Markdown
37 lines
861 B
Markdown
Structured binding declaration 可以把對應的 tuple、pair、vector 展開，讓 code 更好讀。
|
||
|
||
## 展開 tuple
|
||
假設我們有一個 tuple：
|
||
```cpp
|
||
std::tuple<std::string, uint32_t, uint32_t> person{ "John", 32, 170 };
|
||
|
||
auto& [name, age, tall] = person;
|
||
```
|
||
|
||
name 會是 "John"
|
||
age 是 32
|
||
tall 是 170
|
||
|
||
但比較好用的時候還是用來展開 function 的回傳值，假設我們有一個 function 會回傳 tuple：
|
||
```cpp
|
||
std::tuple<std::string, uint32_t, uint32_t> getPersonData(uint32_t id) {
|
||
return std::make_tuple("John", 32, 170);
|
||
}
|
||
|
||
auto [name, age, tall] = getPersonData(id);
|
||
```
|
||
|
||
## 展開 array
|
||
`std::vector` 也是一樣的用法：
|
||
```cpp
|
||
#include <array>
|
||
|
||
std::array<int, 3> my_vec = { 5, 7, 10 };
|
||
auto& [num1, num2, num3] = my_vec;
|
||
```
|
||
|
||
或是：
|
||
```cpp
|
||
float rect[4]{ 5.0f, 6.0f, 120.0f, 200.0f };
|
||
auto& [x, y, w, h] = rect;
|
||
``` |