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POPass member function pointers by argument and store them
 

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    <p>I'm trying to tackle OOP with a little project of mine. I'm trying to create a simple Menu class (terminal-based) to build, show and execute a menu. And this menu should execute functions from a second class Calendar which is the "main" program. </p> <p>Which interface I try to achieve is:</p> <pre><code>int main() { Menu menu; menu.add("Exit program", &amp;Calendar::exit); menu.show(); menu.execute(menu.EXIT); // or just 0 } </code></pre> <p>Which should look something like:</p> <blockquote> <p>CALENDAR MENU</p> <p>0 Exit program</p> </blockquote> <p>What I want to achieve is the add()-method should add a function-pointer to a map&lt;int, function-pointer&gt;. This is where my problem starts. Currently I have a hard-coded array with function-pointers in my execute()-method. Now I want to dynamically add a menu-item with the appropriate function.</p> <pre><code>class Menu { // declaration of function-pointer thingy typedef void (Calendar::*CalendarPtr)(); // will hold the string in the add()-method std::vector&lt;std::string&gt; options_strings; // will hold the integer associated to the appropriate function std::map&lt;int, CalendarPtr&gt; options_map; public: // possible options enum OPTIONS {EXIT}; // shows the menu on-screen void show(); // should add string to vector, function-pointer to map void add(std::string, CalendarPtr); // should execute appropriate function (based on option passed) void execute(OPTIONS option); }; // ... void Menu::add(std::string option, CalendarPtr) // what doesn't work obviously { // adding string to vector options_strings.push_back(option); // Just binding the latest entry of the string to the function-pointer int index = options_strings.size(); // TRYING to add function-pointer to map options_map.insert(std::pair&lt;int, CalendarPtr&gt;(index, CalendarPtr)); } Menu::execute(OPTIONS option) // enum declared as public in class { int option = EXIT; // or 0 CalendarPtr cptr[] = {&amp;Calendar::exit}; Calendar* cal; if (option &gt;= 0 &amp;&amp; option &lt; static_cast&lt;int&gt;(options_strings.size())) (cal-&gt;*cptr[option])(); } </code></pre> <p>The insert-line currently gives:</p> <blockquote> <p>../src/Menu.cpp:24: error: expected primary-expression before ';' token</p> </blockquote> <p>which means that my use of function-pointers isn't right, but what is the right way? How would I declare the wanted add()-method (so which parameters), how would I insert the function-pointers in the map and how would I call the desired item in the map with my execute()-method?</p> <p>If something is not clear, please say it and I'll try to explain it better/different :)</p> <p>Thanks in advance!</p> <p><strong>EDIT 1:</strong></p> <p>I changed</p> <pre><code>void Menu::add(std::string option, CalendarPtr) // ... options_map.insert(std::pair&lt;int, CalendarPtr&gt;(index, CalendarPtr)); </code></pre> <p>to</p> <pre><code>void Menu::add(std::string option, CalendarPtr cptr) // ... options_map.insert(std::pair&lt;int, CalendarPtr&gt;(index, cptr)); </code></pre> <p>But how do you "call" the function at the inserted (say index 0) position? options_map0; doesn't work...</p> <p><strong>EDIT 2:</strong></p> <p>It inserted the function-pointer with index 1 ;) Problem solved!</p> <p><strike>I get an error when I have this method:</p> <pre><code>void Menu::execute(OPTIONS option) { Calendar c; Calendar* calendar = &amp;c; CalendarPtr cptr = options_map.at(0); (*calendar.*cptr)(); } </code></pre> <blockquote> <p>terminate called after throwing an instance of 'std::out_of_range' what(): map::at</p> </blockquote> <p>So I conclude that the insert failed, why so?</strike></p>
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    1. COWhich is line 24?
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    2. COYou haven't given your `CalendarPtr` argument a name. Is this your *actual* code?
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    3. CO@Oli Charlesworth, line 24 is options_map.insert(std::pair<int, CalendarPtr>(index, CalendarPtr));
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