c++ - 填充 C++ 结构 vector 的首选方法

Question

备选方案 1，重用临时变量:

Sticker sticker;
sticker.x = x + foreground.x;
sticker.y = foreground.y;
sticker.width = foreground.width;
sticker.height = foreground.height;
board.push_back(sticker);

sticker.x = x + outline.x;
sticker.y = outline.y;
sticker.width = outline.width;
sticker.height = outline.height;
board.push_back(sticker);

备选方案 2，限定临时变量的范围:

{
 Sticker sticker;
 sticker.x = x + foreground.x;
 sticker.y = foreground.y;
 sticker.width = foreground.width;
 sticker.height = foreground.height;
 board.push_back(sticker);
}

{
 Sticker sticker;
 sticker.x = x + outline.x;
 sticker.y = outline.y;
 sticker.width = outline.width;
 sticker.height = outline.height;
 board.push_back(sticker);
}

方案三，直接写入 vector 内存:

{
 board.push_back(Sticker());
 Sticker &sticker = board.back();
 sticker.x = x + foreground.x;
 sticker.y = foreground.y;
 sticker.width = foreground.width;
 sticker.height = foreground.height;
}

{
 board.push_back(Sticker());
 Sticker &sticker = board.back();
 sticker.x = x + outline.x;
 sticker.y = outline.y;
 sticker.width = outline.width;
 sticker.height = outline.height;
}

您更喜欢哪种方法？

编辑:为了便于讨论，假设必须在构造函数之外逐一进行赋值

Answer 1

我的选择 - 为 Sticker 提供一个接受参数的构造函数。然后:

board.push_back( Sticker( outline.x, foo.bar, etc. ) );  

编辑:说明构造函数参数名称的代码:

#include <iostream>
using namespace std;

struct S {
    int a, b;
    S( int a, int b ) : a(a), b(b) {
    }
};

int main() {    
    S s( 1, 2);
    cout << s.a << " " << s.b << endl;
}