在 mongodb/flask 中存储用户喜欢的食谱

Question

Creating a recipe sharing page as a school project in flask with mongodb. I would like to store which recipes that users have liked so that they cannot like them more than oncew. I originally did it in session then realised you can delete or it will expire etc. Thought of storing the _id of the recipes they liked but couldnt figure out how to store many of them and look through them. Any ideas im not thinking of here? Im quite new so i apologise if this is simple. Thank you!!

Answer 1

I am also new to MongoDB. How about storing recipeID in an array field (ex: likedRecipes ), which is a part of Users collection? Something like below:

Users collection:

[
    {
        'user' : 1,
        'likedRecipes': [
            1,
            4,
            5
        ]
    },
    {
        'user' : 2,
        'likedRecipes': [
            3,
            4,
            2
        ]
    }
]

Recipes collection:

[
    {
        'id': 1,
        'name': 'Samosa',
        'ingredients': [...]
    },
    {
        'id': 2,
        'name': 'Paneer Tikka',
        'ingredients': [...]
    }
    ...,
    ...,
]

In the UI, when you are displaying a recipe for a user, you can make a check whether the user has already liked the recipe or not. If the user has already liked, then you can allow the user to unlike, else allow the user to like.

Below is the query to get whether the user has liked a particular recipe or not:

db.user.aggregate([
    {
        $match: {
            user: 2
        }
    },
    {
        $project: {
            isLiked: {
                $cond: [
                    {$in: [1, "$likedRecipes"]},
                    true,
                    false
                ]
            }
        }
    }
])

Explanation:

1. You need to match the logged in user's id , so $match operator is used.
2. $cond is used to check whether the currently displaying recipe's id is present in the logged in user's likedRecipe array, if yes then return true else return false .
3. Use the $project operator to put the above result in a new field called isLiked .

I hope it helps.