如何在猫鼬模式中表示范围？

Question

背景

假设我正在做一个关于你可以购买的水果的模式。在这个模式中，水果有一个价格范围：

let fruit = {
    name: "banana",
    price: {
        currency: "EUR",
        range: [2, 10]
    }
};

为了实现保存上述对象，我尝试使用以下架构：

let fruitSchema = {
    name: {type: String, required: true},
    price: {
        currency: {type: String, required: true},
        range: [{
            type: Number,
            min: 0
        }],
        validate: [arraySize]
    }
};

const arraySize = function arrayLimit(val) {
  return val.length === 2;
};

问题：

我对范围部分的解决方案感觉笨拙，过于复杂，并且不检查最大范围值是否大于最小范围值，即不检查是否 10 > 2。

题：

• 您将如何在 mongoose 的模式中实现价格范围？

Answer 1

My solution

I decided to have both values in my Schema separately, like in the example bellow:

income: {
    currency: { type: String },
    range: {
        min: { type: Number, min: 0 },
        max: { type: Number, min: 0 }
    }
}

Problem

However, now I am left with a problem. How to check that my MAX >= MIN at all times, and that MIN <= MAX ??

Given that nor MIN nor MAX are mandatory, one can have an object with just an upper range, or just a lower one.

Enter Custom Validators

To fix this validation issue, I used custom validator functions. Validators were the missing piece in the puzzle, and allowed me to enforce max and min restrictions:

validate object for min:

validate: {
    validator: function(val){
        const currMax = this.target.income.range.max;
        return (currMax !== undefined ? val <= currMax : true);
    },
    message: "The MIN range with value {VALUE} must be <= than the max range!"
}

validate object for max:

validate: {
    validator: function(val) {
        const currMin = this.target.income.range.min;
        return (currMin !== undefined ? val >= currMin : true);
    },
    message: "The MAX range with value {VALUE} must be >= than the min range!"
}

Final result

Thus, the final result is as follows:

income: {
    currency: { type: String },
    range: {
        min: { 
            type: Number, min: 0,
            validate: {
                validator: function(val){
                    const currMax = this.target.income.range.max;
                    return (currMax !== undefined ? val <= currMax : true);
                },
                message: "The MIN range with value {VALUE} must be <= than the max range!"
            }
        },
        max: { 
            type: Number, min: 0,
            validate: {
                validator: function(val) {
                    const currMin = this.target.income.range.min;
                    return (currMin !== undefined ? val >= currMin : true);
                },
                message: "The MAX range with value {VALUE} must be >= than the min range!"
            }
        }
    }
}

Going further

This solution is nice, shows advanced knowledge and does the requirements. In you try to insert an object where MIN > MAX, you will have a nice error message with the VALUE being inserted.

However, I have the following questions / suggestions for improvement, that I didn't add because I don't yet know how to do:

1. The validator will keep inconsistent objects from being inserted. However, when it does not prevent bad UPDATES, i.e., the following example will work on an object with MIN = 10:

   ObjModel.update( { _id: "58dd26b5476664e33eec4b93" }, { $set: {"income.range.max": 1}} );

To do updates on objects using validators, you must use the save method, and follow the convention described at the end of the mongoose docs.

Model.findOne({ name: 'borne' }, function (err, doc){
  doc.name = 'jason borne';
  doc.visits.$inc();
  doc.save();
});

Which will trigger the validator as expected.

2. In the functions to check MIN and MAX, you can print the value being evaluated using {VALUE}. However, can you use other values of the object? When comparing MIN and MAX, it would be useful to print the value being evaluated as well as the values it is being compared to.

Hope it helps, and inspires!