STL向量，迭代器和插入（C ++）

本文介绍了STL向量，迭代器和插入（C ++）的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个向量的迭代器传递的方法。 在这个方法中，我想添加一些元素到向量中，但是我不知道这是否可能，当只有迭代器

void GUIComponentText :: AddAttributes（vector< GUIComponentAttribute *> :: iterator begin，vector< GUIComponentAttribute *> :: iterator end） { for > :: iterator i = begin; i！= end; ++ i） { GUIComponentAttribute& attrib = *（* i） //这里是分析的GUIComponentAttribute对象 - 如果出现 //特殊类型的对象，我想向向量中添加一些元素} }

解决方案

首先，你必须改变界面。给定两个迭代器，没有办法返回到它们引用的容器;所以如果你想修改容器，你必须传递一个引用， ie：

void GUIComponentText :: AddAttributes（ std :: vector< GUIComponentAttribute *>& attributes） { for（std :: vector< GUIComponentAttribute *> :: iter = attributes.begin（）; iter！= attributes.end（）; ++ iter） { // ... } $ b b}

完成后：插入可以使迭代器无效。所以它取决于你想插入。如果你想在当前的位置插入： std :: vector<> :: insert 单个元素返回一个迭代器元素，这是插入你的元素之前，所以你可以将它分配给你的迭代器，调整（如果必要），并继续：

code> iter = attributes.insert（iter，newAttribute）; ++ iter; //返回我们的位置...

如果您要追加（ push_back ），问题有点复杂; 你需要计算偏移量，然后重建迭代器：

size_t offset = iter - attributes.begin ; attributes.push_back（nweAttribute）; iter = attributes.begin（）+ offset;

在这种情况下，使用 size_t 和 [] ，而不是迭代器。

I have a method to which a vector's iterator is passed. In this method I'd like to add some elements into the vector, but I am not sure whether this is possible when having only the iterator

void GUIComponentText::AddAttributes(vector<GUIComponentAttribute*>::iterator begin, vector<GUIComponentAttribute*>::iterator end) { for (vector<GUIComponentAttribute*>::iterator i = begin; i != end; ++i) { GUIComponentAttribute &attrib = *(*i); // Here are the GUIComponentAttribute objects analyzed - if an object of a // special kind appears, I would like to add some elements to the vector } }

Thanks Markus

解决方案

First, you'll have to change the interface. Given two iterators, there's no way to get back to the container to which they refer; so if you want to modify the container, you'll have to pass a reference to it, i.e.:

void GUIComponentText::AddAttributes( std::vector<GUIComponentAttribute*>& attributes ) { for ( std::vector<GUIComponentAttribute*>::iter = attributes.begin(); iter != attributes.end(); ++ iter ) { // ... } }

Having done that: insertion can invalidate iterators. So it depends on where you want to insert. If you want to insert at the current position: std::vector<>::insert of a single element returns an iterator to that element, which was inserted before your element, so you can assign it to your iterator, adjust (if necessary), and continue:

iter = attributes.insert(iter, newAttribute); ++ iter; // Return to where we were...

If you're appending (push_back), the problem is a bit more complex; you need to calculate the offset, then reconstruct the iterator:

size_t offset = iter - attributes.begin(); attributes.push_back( nweAttribute ); iter = attributes.begin() + offset;

In this case, it is probably simpler to iterate using a size_t and [], rather than an iterator.