##实战c++中的vector系列--creating vector of local structure、vector of structs initialization 之前一直没有使用过`vector<struct>，现在就写一个简短的代码：  ` ~~~ #include <vector> #include <iostream> int main() { struct st { int a; }; std::vector<st> v; v.resize(4); for (std::vector<st>::size_type i = 0; i < v.size(); i++) { v.operator[](i).a = i + 1; // v[i].a = i+1; } for (int i = 0; i < v.size(); i++) { std::cout << v[i].a << std::endl; } } ~~~ 用VS2015编译成功，运行结果：  1  2  3  4 但是，这是C++11之后才允许的，之前编译器并不允许你写这样的语法，不允许vector容器内放local structure。 更进一步，如果struct里面有好几个字段呢？ ~~~ #include<iostream> #include<string> #include<vector> using namespace std; struct subject { string name; int marks; int credits; }; int main() { vector<subject> sub; //Push back new subject created with default constructor. sub.push_back(subject()); //Vector now has 1 element @ index 0, so modify it. sub[0].name = "english"; //Add a new element if you want another: sub.push_back(subject()); //Modify its name and marks. sub[1].name = "math"; sub[1].marks = 90; sub.push_back({ "Sport", 70, 0 }); sub.resize(8); //sub.emplace_back("Sport", 70, 0 ); for (int i = 0; i < sub.size(); i++) { std::cout << sub[i].name << std::endl; } } ~~~ 但是上面的做法不好，我们应该先构造对象，后进行push_back 也许更加明智。  subject subObj;  subObj.name = s1;  sub.push_back(subObj); 这个就牵扯到一个问题，为什么不使用emplace_back来替代push_back呢，这也是我们接下来讨论 话题。