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POC++ Using a class template argument as a template argument for another type
 

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  1. POC++ Using a class template argument as a template argument for another type
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    <p>I'm having this problem while writing my own HashTable. It all works, but when I try to templatize the thing, it gave me errors. I recreated the problem as follows: </p> <p>THIS CODE WORKS:</p> <pre><code>typedef double Item; class A { public: A() { v.push_back(pair&lt;string, Item&gt;("hey", 5.0)); } void iterate() { for(Iterator iter = v.begin(); iter != v.end(); ++iter) cout &lt;&lt; iter-&gt;first &lt;&lt; ", " &lt;&lt; iter-&gt;second &lt;&lt; endl; } private: vector&lt;pair&lt;string, double&gt; &gt; v; typedef vector&lt; pair&lt;string, double&gt; &gt;::iterator Iterator; }; </code></pre> <p>THIS CODE DOES NOT: </p> <pre><code>template&lt;typename ValueType&gt; class B { public: B(){} void iterate() { for(Iterator iter = v.begin(); iter != v.end(); ++iter) cout &lt;&lt; iter-&gt;first &lt;&lt; ", " &lt;&lt; iter-&gt;second &lt;&lt; endl; } private: vector&lt;pair&lt;string, ValueType&gt; &gt; v; typedef vector&lt; pair&lt;string, ValueType&gt; &gt;::iterator Iterator; }; </code></pre> <p>the error messages: g++ -O0 -g3 -Wall -c -fmessage-length=0 -omain.o ..\main.cpp</p> <p>..\main.cpp:50: error: type <code>std::vector&lt;std::pair&lt;std::string, ValueType&gt;, std::allocator&lt;std::pair&lt;std::string, ValueType&gt; &gt; &gt;' is not derived from type</code>B'</p> <p>..\main.cpp:50: error: ISO C++ forbids declaration of `iterator' with no type</p> <p>..\main.cpp:50: error: expected `;' before "Iterator"</p> <p>..\main.cpp: In member function `void B::iterate()':</p> <p>..\main.cpp:44: error: `Iterator' was not declared in this scope</p> <p>..\main.cpp:44: error: expected `;' before "iter"</p> <p>..\main.cpp:44: error: `iter' was not declared in this scope</p> <p>Does anybody know why this is happening? Thanks! </p>
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