Question

我在领域Product和ProductType中有两个实体。产品与产品类型有一对多的关系。

产品实体一对多

ProductType实体

import Foundation
import RealmSwift

class Product: Object{
    dynamic var productName = ""
    let productTypeList = List<ProductType>() 
}

我的目标是选择包含ProductType typeName的所有产品，例如“Electronics”。如果像这样一对一的关系，我可以轻松地做到这一点

产品实体一对一

import Foundation
import RealmSwift

class ProductType: Object{   
  dynamic var typeName: String = ""
  dynamic var typeLogoUrl: String = ""
}

查询示例

import Foundation
import RealmSwift

class Product:Object{
    dynamic var productName = ""
    dynamic var productType : ProductType? 
}

如何使用一对多版本的Product类进行查询？

Answer 1

您可以使用子查询并检查与名称匹配的列表中的productTypes的计数是否大于0.

let rmProducts = realm.objects(Product.self).filter("SUBQUERY(productTypeList, $type, $type.typeName == %@).@count>0",productTypeName)

我已在以下测试集上运行查询并获得预期结果：

class Product:Object{
    dynamic var productName = ""
    var productTypeList = List<ProductType>()
}

class ProductType  : Object{
    dynamic var typeName: String = ""
    dynamic var typeLogoUrl: String = ""
}

let types = [ProductType(value: ["typeName":"Electronics","typeLogoUrl":"url"]),ProductType(value: ["typeName":"a","typeLogoUrl":"url"]),ProductType(value: ["typeName":"Electronics","typeLogoUrl":"a"]),ProductType(value: ["typeName":"b","typeLogoUrl":"url"])]

let prod1 = Product()
prod1.productName = "a"
prod1.productTypeList = List([types[0],types[1]])
let prod2 = Product()
prod2.productName = "b"
prod2.productTypeList = List([types[3],types[1]])
let prod3 = Product()
prod3.productName = "c"
prod3.productTypeList = List([types[2],types[1]])
var prod4 = Product()
prod4.productName = "d"
prod4.productTypeList = List([types[1]])

try! realm.write {
    realm.add(types)
    realm.add([prod1,prod2,prod3,prod4])
}

let productTypeName = "Electronics"
let predicate = NSPredicate(format: "productType.typeName == %@", productTypeName)
let rmProducts = realm.objects(Product.self).filter("SUBQUERY(productTypeList, $type, $type.typeName == %@).@count>0",productTypeName)
print(rmProducts) //rmProducts contains prod1 and prod3 as expected

Answer 2

对于像这样的简单查询，您需要ANY修饰符：

realm.objects(Product.self).filter("ANY productTypeList.typeName == %@", productTypeName)

只有在每个要匹配的子对象上需要多个条件时，才需要在另一个答案中建议SUBQUERY。例如，如果您想查找包含指定类型的项目的Products，其网址以https://开头，您将使用SUBQUERY：

realm.objects(Product.self).filter("SUBQUERY(productTypeList, $type, $type.typeName == %@ AND $type.typeLogoUrl BEGINSWITH 'https://').@count > 0", productTypeName)

Realm Swift选择与一对多关系实体中的一个字段匹配的所有值

2 个答案: