C ++：使方法每次返回相同的对象 [英] C++: Making method return the same object every time

问题描述

我想有一个函数加载一个文件（在这种情况下是一个OpenGL纹理），但实际上只加载文件一次，每次调用后，它只是返回它最初加载的东西。

I would like to have a function that loads a file (in this case an OpenGL texture), but only actually loads the file once, and every time it is called after that it just returns what it initially loaded.

这是一个很好的方法吗？

What would be a good way to do this?

谢谢。

推荐答案

您需要一些地方来存储该状态。这可以在一个对象内或作为一个静态变量。让我们说：

You need some place to store that state. That can be either inside an object or as a static variable. Let's say:

class TextureLoader {
public:
    TextureLoader() {}
    GLuint loadTexture(std::string const & filename){
        std::map<std::string, GLuint>::iterator it = m_loadedTextures.find(filename);
        if(it == m_loadedTextures.end()){
            GLuint id = load(filename);
            m_loadedTextures[filename] = id;
            return id;
        }
        else{
            return it->second;
        }
    }
    ~TextureLoader(){
        // iterate and delete textures
    }
private:
    GLuint load(std::string const & filename){
        // real loading
    }
    std::map<std::string, GLuint> m_loadedTextures;
};

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