与向量成员的全球结构

Question

为什么这个简单的代码块未编译

//using namespace std; 
struct test { 
    std::vector<int> vec; 
}; 
test mytest; 

void foo { 
    mytest.vec.push_back(3); 
} 

int main(int argc, char** argv) { 
    cout << "Vector Element" << mytest.vec[0] << endl; 
    return 0; 
} 

我收到以下错误：

vectorScope.cpp:6:5: error: ‘vector’ in namespace ‘std’ does not name a type 

vectorScope.cpp:11:6: error: variable or field ‘foo’ declared void 

vectorScope.cpp:11:6: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x [enabled by default] 

vectorScope.cpp:12:12: error: ‘struct test’ has no member named ‘vec’ 

vectorScope.cpp:12:28: error: expected ‘}’ before ‘;’ token 

vectorScope.cpp:13:1: error: expected declaration before ‘}’ token 

谢谢

穆斯塔法

Answer 1

你需要包含矢量头文件

#include <vector> 
#include <iostream> 

struct test { 
    std::vector<int> vec; 
}; 
test mytest; 

void foo() { 
    mytest.vec.push_back(3); 
} 

int main(int argc, char** argv) 
{ 
    foo(); 
    if (!mytest.vec.empty()) // it's always good to test container is empty or not 
    { 
    std::cout << "Vector Element" << mytest.vec[0] << std::endl; 
    } 
    return 0; 
} 

Answer 2

请记住，包括相应的文件：

#include <vector> 

Answer 3

你缺少<vector>头。

#include <vector> 

Answer 4

如果您的代码示例已完成，则您未包含矢量标头或iostream。还您的FOO功能被错误地声明无（）为参数：

#include <vector> 
#include <iostream> 

using namespace std; 
struct test { 
    std::vector<int> vec; 
}; 
test mytest; 

void foo() { 
    mytest.vec.push_back(3); 
} 

int main(int argc, char** argv) { 
    cout << "Vector Element" << mytest.vec[0] << endl; 
    return 0; 
} 

此外，您的下标在索引0处，其是未定义的行为空载体。你可能想在做之前先调用foo（）？