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POStoring struct instances in a std::map
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copied!<p>I'm trying to map some structs to some other instances, like this:</p> <pre><code>template <typename T> class Component { public: typedef std::map<EntityID, T> instances_map; instances_map instances; Component() {}; T add(EntityID id) { T* t = new T(); instances[id] = *t; return *t; }; }; </code></pre> <p>Then I use it like this:</p> <pre><code>struct UnitInfos { int owner_id; int health; float x, y; }; class LogicComponent : public Component<UnitInfos> {}; </code></pre> <p>The problem is that when it later retrieve data later on, like this:</p> <pre><code>comp.instance[id]; </code></pre> <p>I get a breand new object with properties initialized at default values. </p> <p>Is there something inherently wrong with this piece of code, or am I leaving out information about the problem?</p> <hr> <p>As per @aaa suggestion, i change the code to </p> <pre><code>typedef std::map<EntityID, T> instances_map; instances_map instances; T& add(EntityID id) { instances[id] = T(); return instances[id]; }; </code></pre> <p>but when I access it</p> <pre><code>UnitInfos &info = logic_c.instances[id]; </code></pre> <p>the value of info.x is still 0. Any pointers?</p> <hr> <p>The problem was how I stored the reference to LogicComponent in another class. using <code>LogicComponent logic_c;</code> instead of <code>LogicComponent& logic_c;</code>. It now works, but I'm storing pointers in the map (instead of @aaa's suggestion). Is this a bad idea?</p>

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