Question

我从路径模式（db / collection / _id）中获取MongoDB中的值，并尝试将数据插入到地图中（Key = _id，value = full path）。但是，当我试图通过将键值传递给函数map.find（）来查找某些地图数据时，即使该键存在，它也会返回map.end（）。

以下是我实施的代码，请仔细阅读并告知我出错的地方。

        class myStructure {
            std::vector<string> arr;
        public:
            std::map<std::string, std::string> myMap;

        public:
            void add(char *ptr, size_t len, FILE *stream) {
                std::string key;
                unsigned found;

                while (getline(&ptr, &len, stream) != -1) {
                    std::string path(ptr);
                    found = path.find_last_of("/\\");
                    key = path.substr(found + 1);
                    myMap[key] = path;
                }
        // Iterating entire Map
                std::map<string, string>::iterator its1 = myMap.begin();
                std::cout << "myMap contains:\n";;
                for (its1 = myMap.begin(); its1 != myMap.end(); ++its1)
                    std::cout << its1->first << " => " << its1->second << '\n';
  // Output
//59dd9db3b3defb36a894a0f1 => /test/restaurants/59dd9db3b3defb36a894a0f1      
                std::string key_to_erase;
                std::cout << "Enter Key value to remove:" << std::endl;
                std::cin >> key_to_erase;
        //Erasing provided key value
                std::map<std::string, std::string>::iterator iit = myMap.find(key_to_erase);

                if (iit == myMap.end()) {
                    std::cout << "key not found\n";
                }
                    // Check if iterator is valid.
                else {
                    // Remove the element pointed by iterator
                    myMap.erase(key_to_erase);
                    std::cout << "Element Removed" << std::endl;
                }
            }

        };

        int main(int, char**)
        {
            FILE *fpipe;
            std::string file;
            char *command = "/usr/bin/mongo --eval \"db.getSiblingDB(\\\"admin\\\").runCommand({ \\\"listDatabases\\\": 1 }).databases.forEach(function(database) {db = db.getSiblingDB(database.name);cols = db.getCollectionNames();cols.forEach(function(collectionName) {collection=db.getCollection(collectionName);keys=collection.find();keys.forEach(function(key){print(\\\"/\\\"+db+\\\"/\\\"+collectionName+\\\"/\\\"+key._id);});});});\"";
    //input values
    /*test/restaurants/59dd9db4b3defb36a894cd31
    test/restaurants/59dd9db4b3defb36a894cd32
    test/restaurants/59dd9db4b3defb36a894cd33
    test/restaurants/59dd9db4b3defb36a894cd34*/

            char *ptr = NULL;

            size_t len;
            std::array<char, 128> buffer;
            FILE *stream = popen (command, "r");
            myStructure ds;
            ds.add(ptr, len, stream);


        }

Answer 1

如前所述，我们在getline(&ptr, &len, stream)的密钥中获取换行符，并且在删除该代码后，用户条目工作正常。我使用下面的代码来纠正删除换行符

key.erase(std::remove(key.begin(), key.end(), '\n'), key.end());

map.find（）没有找到关键的c ++

1 个答案: