使用包含过滤器在环回中加入两个模型 [英] Joining two models in loopback using include filter

问题描述

我有两个型号的购买和产品，而且productId对两者都很常见。

I have two models Purchase and Products, and productId is common for both.

我需要从productId的产品型号中找到productDetails。

I need to find the productDetails from product model for a purchaseId.

所以我在Purchase模型中创建了一个名为getProductDetails的自定义端点。

So I have created a custom endpoint in Purchase model, called getProductDetails.

这就是我试图查询模型的方法。

This is how I am trying to query the models.

         Purchase.find({
            "filter": {
                include: {
                    relation: 'Product',
                    scope: {
                        fields: ['productDesc'],
                    }
                }
            },
           where:{
                id:purchaseId
            },

我的关系是
购买belongsTo产品，foreignKey是productId

My relation is Purchase belongsTo Product, foreignKey being productId

产品有很多购买

但即使我做上述查询，我​​也是不要在查询结果中获得productDesc

我的模型关系是否错误？

推荐答案

假设产品和购买模型定义如下：

Assuming Product and Purchase models defined as follows:

product.json

product.json

{
  "name": "Product",
  "base": "PersistedModel",
  "idInjection": true,
  "properties": {
    "productDesc": {
      "type": "string",
      "required": false
    }
  },
  "validations": [],
  "relations": {
    "purchases": {
      "type": "hasMany",
      "model": "Purchase",
      "foreignKey": "productId"
    }
  },
  "acls": [],
  "methods": {}
}

purchase.json

purchase.json

{
  "name": "Purchase",
  "base": "PersistedModel",
  "idInjection": true,
  "properties": {},
  "validations": [],
  "relations": {
    "product": {
      "type": "belongsTo",
      "model": "Product",
      "foreignKey": "productId"
    }
  },
  "acls": [],
  "methods": {}
}

我已经调整了你的查询：

I have adjusted your query like this:

let product = await Purchase.find({
      include: {
        relation: 'product',
        scope: {
          fields: ['productDesc']
        }
      },
      where: {
        id: 1
      }
    })

注意：使用ES6和ES7，但可以很容易地重写为ES5

Note: ES6 and ES7 used, but it can be easily rewriten to ES5

您必须使用 toJSON 转换返回的模型将相关项放入普通JSON对象的实例。

You have to use toJSON to convert the returned model instance with related items into a plain JSON object.

我不确定，为什么要创建新端点。环回提供的应该足够了。

I'm not sure, why are you creating a new endpoint though. The ones provided by loopback should be sufficient.

例如

GET /Purchases/{id}/product

或

GET /Purchases/{id}

带过滤器

{ "include": [ "product"]}

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