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POC++ Decorator pattern
 

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    <p>I've a <em>vector</em> and several classes (located in separate files) to modify the one.<br> I want to have global access to the <code>std::vector</code>, but only within the derived classes when each call stores the result of previous and the last object should return the total result</p> <p>Could you explain how to build a high-performance interface using Decorator pattern with <code>std::vector</code>?<br> I may be wrong, and may need other pattern.</p> <pre><code>// A.h class A () { public : vector&lt;int&gt; set(vector&lt;int&gt; &amp;vec); //return total result vector&lt;int&gt; get() { return vector; } }; // B.h class B () { //add new elements into vector //for example, add 2,3,4 }; // C.h class C () { //remove some elements from vector //for example, remove last element }; //... // main.cpp #include "A.h" #include "B.h" #include "C.h" int main () { vector&lt;int&gt; set; set.push_back(1); //1 C obj(new B(new A())); obj.set(set); obj.get(); // stores 1,2,3 (added by classes A, B, C) } </code></pre> <p>So, I don't want to do like this:</p> <pre><code>vector&lt;int&gt; set1; set1.push_back(1); A *A_init; A_init-&gt;set(set1); //add 1 vector&lt;int&gt; set2 = A_init-&gt;get(); B *B_init; B_init-&gt;set(set2); //add 2, stores 1,2 vector&lt;int&gt; set3 = B_init-&gt;get(); C *C_init; C_init-&gt;set(set3); //add 3, stores 1,2,3 vector&lt;int&gt; set4 = C_init-&gt;get(); /.. </code></pre> <p>And I want to do like this:</p> <pre><code>vector&lt;int&gt; set; set.push_back(1); C obj(new B(new A())); obj.set(set); obj.get(); // stores 1,2,3 </code></pre> <p>I've a simple impementation of a pattern Decorator.<br> But it is not quite what I need ((</p> <pre><code>#include &lt;iostream&gt; #include &lt;memory&gt; class A { public: virtual void operation() = 0; }; class Component : public A { public: virtual void operation() { std::cout&lt;&lt;"World!"&lt;&lt;std::endl; } }; class B : public A { std::unique_ptr&lt;A&gt; add; public: B(A *component): add(component) {} virtual void operation() { std::cout &lt;&lt; ", "; add-&gt;operation(); } }; class C : public A { std::unique_ptr&lt;A&gt; add; public: C(A *component): add(component) {} virtual void operation() { std::cout &lt;&lt; "Hello"; add-&gt;operation(); } }; int main() { C obj(new B(new Component())); obj.operation(); // prints "Hello, World!\n" return 0; } </code></pre> <p>PS: Sorry for not so clear explanation, because I don't know English so well</p>
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    1. COCould you try and rephrase the question(s?) ? It is unclear to me what is being asked. At its simplest, are you wanting to sum the elements of `vector<int>` or something else entirely?
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    2. COYour first block of code has some serious issues, such as an uninitialized `init` variable.
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    3. CO@hmjd, I want to modify `vector<int>` (add or remove element) in global scope (or something like that), but using several classes and return total result (modified vector).
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