C++ 访问向量内的元素对
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C++ Access an element of pair inside vector
提问by Romaan
I have a vector with each element being a pair. I am confused with the syntax. Can someone please tell me how to iterate over each vector and in turn each element of pair to access the class.
我有一个向量，每个元素都是一对。我对语法感到困惑。有人可以告诉我如何遍历每个向量，然后依次遍历 pair 的每个元素来访问该类。
std::vector<std::pair<MyClass *, MyClass *>> VectorOfPairs;
Also, please note, I will be passing the values in between the function, hence VectorOfPairs with be passed by pointer that is *VectorOfPairs in some places of my code.
另外，请注意，我将在函数之间传递值，因此 VectorOfPairs 在我的代码的某些地方由指针传递，即 *VectorOfPairs。
Appreciate your help. Thanks
感谢你的帮助。谢谢
回答by Benj
This should work (assuming you have a C++11 compatible compiler)
这应该可以工作（假设你有一个 C++11 兼容的编译器）
for ( auto it = VectorOfPairs.begin(); it != VectorOfPairs.end(); it++ )
{
// To get hold of the class pointers:
auto pClass1 = it->first;
auto pClass2 = it->second;
}
If you don't have autoyou'll have to use std::vector<std::pair<MyClass *, MyClass *>>::iteratorinstead.
如果你没有，auto你将不得不使用std::vector<std::pair<MyClass *, MyClass *>>::iterator。
回答by John Dibling
Here is a sample. Note I'm using a typedef to alias that long, ugly typename:
这是一个示例。请注意，我使用 typedef 为那个又长又丑的 typename 取别名：
typedef std::vector<std::pair<MyClass*, MyClass*> > MyClassPairs;
for( MyClassPairs::iterator it = VectorOfPairs.begin(); it != VectorOfPairs.end(); ++it )
{
MyClass* p_a = it->first;
MyClass* p_b = it->second;
}
回答by Praetorian
Yet another option if you have a C++11 compliant compiler is using range based forloops
如果你有一个 C++11 兼容的编译器，另一个选择是使用基于范围的for循环
for( auto const& v : VectorOfPairs ) {
// v is a reference to a vector element
v.first->foo();
v.second->bar();
}
