CosmicMind / Graph：搜索特定的相关实体

Question

大家好，

寻找对来自CosmicMind（CoreData）的Graph包装框架https://github.com/CosmicMind/Graph的支持。

不幸的是，除了绝对的基础知识之外，很少有文档（尽管b.t.w中似乎有很多非常强大的概念）。

我想知道是否有人可以 - 请帮助我如何选择/过滤1：N关系中的实体。

鉴于以下结构......

import Graph

let graph = Graph()
graph.clear()

let sectionA = Entity(type: "Section")
sectionA["id"] = 12
sectionA["name"] = "SectionA"

let sectionB = Entity(type: "Section")
sectionB["id"] = 2
sectionB["name"] = "SectionB"

let unitA = Entity(type: "Unit")
unitA["id"] = 122
unitA["name"] = "UnitA"
unitA["isExpensive"] = false
unitA.is(relationship: "UnitOfSection").of(sectionA)

let unitB = Entity(type: "Unit")
unitB["id"] = 19
unitB["name"] = "UnitB"
unitB["isExpensive"] = false
unitB.is(relationship: "UnitOfSection").of(sectionB)

let unitC = Entity(type: "Unit")
unitC["id"] = 7
unitC["name"] = "UnitC"
unitC["isExpensive"] = true
unitC.is(relationship: "UnitOfSection").of(sectionA)

let unitD = Entity(type: "Unit")
unitD["name"] = "UnitD"
unitD["isExpensive"] = true
unitD["id"] = 4
unitD.is(relationship: "UnitOfSection").of(sectionA)

graph.sync()

let unitsSearch = Search<Entity>(graph: graph).for(types: "Unit")
let units = unitsSearch.sync()

...我想只得到那些与sectionA有“UnitOfSection”关系的实体，它们的属性为“isExpensive”，值为false。

知道怎么做到这一点？

谢谢+祝福

Answer 1

这应该工作：

let units = Search<Entity>(graph: graph).for(types: "Unit").sync().filter { entity in
    (entity["isExpensive"] as? Bool) == false && 
    entity.relationship(types: "UnitOfSection").contains(where: { relationship in
        relationship.object == sectionA
    })
}

我们做的是：

1. 获取所有“单位”实体
2. 过滤具有isExpensive = false的实体
3. 并获取每个实体的“UnitOfSection”关系，并测试该关系的对象是否为sectionA