blocks|key|1736237|text|问题的解决方案不是创建您自己的迭代器，而是使用现有的STL容器和迭代器。将每个形状中的点存储在一个类似向量的容器中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1736238|class+Shape+{
++++private:
++++vector+<Point>+points;|code-block|syntax|javascript|1736239|从那时起，你要做什么取决于你的设计。最好的方法是遍历Shape中的方法中的点。|1736240|for+(vector+<Point>::iterator+i+=+points.begin();+i+!=+points.end();+%2B%2Bi)
++++/*+...+*/|1736241|如果您需要在Shape外部访问点(这可能是设计缺陷的标志)，您可以在Shape中创建方法，这些方法将返回点的迭代器访问函数(在这种情况下，还可以为points容器创建一个公共类型定义)。请看Konrad+Rudolph的回答，了解这种方法的详细信息。|1736242|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The solution to your problem is not the creation of your own iterators, but the use of existing STL containers and iterators. Store the points in each shape in a container like vector.

<pre><code>class Shape {
 private:
 vector &lt;Point&gt; points;
</code></pre>

What you do from then on depends on your design. The best approach is to iterate through points in methods inside Shape.

<pre><code>for (vector &lt;Point&gt;::iterator i = points.begin(); i != points.end(); ++i)
 /* ... */
</code></pre>

If you need to access points outside Shape (this could be a mark of a deficient design) you can create in Shape methods that will return the iterator access functions for points (in that case also create a public typedef for the points container). Look at the answer by Konrad Rudolph for details of this approach.

blocks|key|1521223|text|您可以阅读此ddj+article|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1521224|基本上，继承std::iterator可以为您完成大部分工作。|1521225|entityMap|0|LINK|mutability|MUTABLE|url|http://www.ddj.com/cpp/184401929^0|6|B|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

You can read this <a href="http://www.ddj.com/cpp/184401929" rel="nofollow noreferrer">ddj article</a>

Basically, inherit from std::iterator to get most of the work done for you.

blocks|key|1736311|text|您应该使用Boost.Iterators。它包含许多模板和概念，用于为现有迭代器实现新的迭代器和适配器。我写过an+article+about+this+very+topic；它发表在2008年12月的ACCU杂志上。它讨论了一个(IMO)优雅的解决方案来解决您的问题:使用Boost.Iterators公开对象中的成员集合。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1736312|如果您只想使用stl，Josuttis+book中有一章介绍了如何实现您自己的STL迭代器。|1736313|entityMap|0|LINK|mutability|MUTABLE|url|http://accu.org/index.php/journals/1527|1|http://www.josuttis.com/libbook/^0|1J|W|0|0|B|D|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

You should use Boost.Iterators. It contains a number of templates and concepts to implement new iterators and adapters for existing iterators. I have written <a href="http://accu.org/index.php/journals/1527" rel="noreferrer">an article about this very topic</a>; it's in the December 2008 ACCU magazine. It discusses an (IMO) elegant solution for exactly your problem: exposing member collections from an object, using Boost.Iterators.

If you want to use the stl only, the <a href="http://www.josuttis.com/libbook/" rel="noreferrer">Josuttis book</a> has a chapter on implementing your own STL iterators.

blocks|key|1736390|text|这里的Designing+a+STL+like+Custom+Container是一篇很好的文章，它解释了一些基本的概念，解释了如何设计一个类似STL的容器类以及它的迭代器类。反向迭代器(稍微困难一点)，不过作为练习:-)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1736391|HTH，|1736392|entityMap|0|LINK|mutability|MUTABLE|url|http://accu.org/index.php/journals/389^0|3|11|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

Here <a href="http://accu.org/index.php/journals/389" rel="noreferrer">Designing a STL like Custom Container</a> is an excellent article which explains some of the basic concepts of how an STL like container class can be designed along with the iterator class for it. Reverse iterator (little tougher) though is left as an exercise :-)
HTH,

blocks|key|1521473|text|用C%2B%2B编写自定义迭代器可能相当冗长且难以理解。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1521474|由于我找不到一种最小的方法来编写自定义迭代器，所以我编写了可能会有所帮助的this+template+header。例如，要使Piece类可迭代：|offset|length|style|CODE|1521475|#include+<iostream>
#include+<vector>

#include+"iterator_tpl.h"

struct+Point+{
++int+x;
++int+y;
++Point()+{}
++Point(int+x,+int+y)+:+x(x),+y(y)+{}
++Point+operator%2B(Point+other)+const+{
++++other.x+%2B=+x;
++++other.y+%2B=+y;
++++return+other;
++}
};

struct+Shape+{
++std::vector<Point>+vec;
};

struct+Piece+{
++Shape&+shape;
++Point+offset;
++Piece(Shape&+shape,+int+x,+int+y)+:+shape(shape),+offset(x,y)+{}

++struct+it_state+{
++++int+pos;
++++inline+void+next(const+Piece*+ref)+{+%2B%2Bpos;+}
++++inline+void+begin(const+Piece*+ref)+{+pos+=+0;+}
++++inline+void+end(const+Piece*+ref)+{+pos+=+ref->shape.vec.size();+}
++++inline+Point+get(Piece*+ref)+{+return+ref->offset+%2B+ref->shape.vec[pos];+}
++++inline+bool+cmp(const+it_state&+s)+const+{+return+pos+!=+s.pos;+}
++};
++SETUP_ITERATORS(Piece,+Point,+it_state);
};|code-block|syntax|javascript|1521476|然后你就可以把它当做一个普通的STL容器使用：|1521477|int+main()+{
++Shape+shape;
++shape.vec.emplace_back(1,2);
++shape.vec.emplace_back(2,3);
++shape.vec.emplace_back(3,4);

++Piece+piece(shape,+1,+1);

++for+(Point+p+:+piece)+{
++++std::cout+<<+p.x+<<+"+"+<<+p.y+<<+std::endl;
++++//+Output:
++++//+2+3
++++//+3+4
++++//+4+5
++}

++return+0;
}|1521478|它还允许添加其他类型的迭代器，如const_iterator或reverse_const_iterator。|1521479|我希望它能帮上忙。|1521480|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/VinGarcia/Simple-Iterator-Template/blob/master/README.md^0|0|1R|5|11|K|0|0|0|0|0|G|E|V|M|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@$D|16|E|17|1|18]]|A|$]]|$1|H|3|I|5|J|7|19|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|1A|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|1B|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|1C|8|@$D|1D|E|1E|F|G]|$D|1F|E|1G|F|G]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1H|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

Writing custom iterators in C++ can be quite verbose and complex to understand.

Since I could not find a minimal way to write a custom iterator I wrote <a href="https://github.com/VinGarcia/Simple-Iterator-Template/blob/master/README.md" rel="nofollow noreferrer">this template header</a> that might help. For example, to make the <code>Piece</code> class iterable:

<pre><code>#include &lt;iostream&gt;
#include &lt;vector&gt;

#include "iterator_tpl.h"

struct Point {
 int x;
 int y;
 Point() {}
 Point(int x, int y) : x(x), y(y) {}
 Point operator+(Point other) const {
 other.x += x;
 other.y += y;
 return other;
 }
};

struct Shape {
 std::vector&lt;Point&gt; vec;
};

struct Piece {
 Shape&amp; shape;
 Point offset;
 Piece(Shape&amp; shape, int x, int y) : shape(shape), offset(x,y) {}

 struct it_state {
 int pos;
 inline void next(const Piece* ref) { ++pos; }
 inline void begin(const Piece* ref) { pos = 0; }
 inline void end(const Piece* ref) { pos = ref-&gt;shape.vec.size(); }
 inline Point get(Piece* ref) { return ref-&gt;offset + ref-&gt;shape.vec[pos]; }
 inline bool cmp(const it_state&amp; s) const { return pos != s.pos; }
 };
 SETUP_ITERATORS(Piece, Point, it_state);
};
</code></pre>

Then you would be able to use it as a normal STL Container:

<pre><code>int main() {
 Shape shape;
 shape.vec.emplace_back(1,2);
 shape.vec.emplace_back(2,3);
 shape.vec.emplace_back(3,4);

 Piece piece(shape, 1, 1);

 for (Point p : piece) {
 std::cout &lt;&lt; p.x &lt;&lt; " " &lt;&lt; p.y &lt;&lt; std::endl;
 // Output:
 // 2 3
 // 3 4
 // 4 5
 }

 return 0;
}
</code></pre>

It also allows for adding other types of iterators like <code>const_iterator</code> or <code>reverse_const_iterator</code>.

I hope it helps.

I'm trying to learn C++ so forgive me if this question demonstrates a lack of basic knowledge, you see, the fact is, I have a lack of basic knowledge.

I want some help working out how to create an iterator for a class I have created.

I have a class 'Shape' which has a container of Points. 
I have a class 'Piece' which references a Shape and defines a position for the Shape.
Piece does not have a Shape it just references a Shape.

I want it to seem like Piece is a container of Points which are the same as those of the Shape it references but with the offset of the Piece's position added.

I want to be able to iterate through the Piece's Points just as if Piece was a container itself. I've done a little reading around and haven't found anything which has helped me. I would be very grateful for any pointers.

Creating my own Iterators

容器

我正在努力学习C++，所以如果这个问题表明我缺乏基本知识，请原谅我，你看，事实是，我缺乏基本知识。我需要一些帮助来解决如何为我创建的类创建迭代器。我有一个类'Shape‘，它有一个点的容器。我有一个类‘块’，它引用了一个形状并定义了该形状的位置。块没有形状，它只是引用了一个形状。我希望它看起来像是块是一个点的容器，这些...

问创建我自己的迭代器
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