如何在swift中使用实体关系从核心数据中获取数据？答案

【问题标题】：How to fetch data from core data using Entity relationship in swift?如何在swift中使用实体关系从核心数据中获取数据？
【发布时间】：2016-06-29 03:40:24
【问题描述】：

我有两个实体“Office”和“Employee”

Office Entity 属性是

         officeId - string
          officename - string

Employee Entity 属性是

         employeename - string
         emailid - string

并拥有多对多的关系——办公室与员工的关系是“员工”

                 func SaveData(){

    let entityOffice = NSEntityDescription.entityForName("Office", inManagedObjectContext: context)
    let newoffice = NSManagedObject(entity: entityOffice!, insertIntoManagedObjectContext: context)
    newoffice.setValue("BUI001", forKey: "officeId")
    newoffice.setValue("Home builders", forKey: "officename")


    let entityEmployees = NSEntityDescription.entityForName("Employee", inManagedObjectContext:context)
    let newemploy = NSManagedObject(entity:  entityEmployees!, insertIntoManagedObjectContext: context)

    // Populate Address

   newemploy.setValue("Tom william", forKey: "employeename")

    newemploy.setValue("tomus@yahoo.com", forKey: "emailid")



    // Add Address to Person
   newoffice.setValue(NSSet(object: newemploy), forKey: "staff")

    do {
        try newoffice.managedObjectContext?.save()
    } catch {
        let saveError = error as NSError
        print(saveError)
    }




}

保存数据工作正常。我不知道如何在有关系的实体之间获取。

如何使用“Office”实体的“officeid”获取“Employee”实体中的所有员工数据。提前感谢

【问题讨论】：

标签： ios xcode swift fetch entity-relationship

【解决方案1】：

您需要像这样使用NSPredicate：

let officeId = "BUI001"
let predicate  = NSPredicate(format: "ANY self.staff.officeId == %@", argumentArray: [officeId])
let fetchRequest = NSFetchRequest(entityName: "Employee")
fetchRequest.predicate = predicate

现在使用这个 fetchRequest 和你的 managedContext 来获取所有与 officeId BUI001 相关的员工

【讨论】：

【解决方案2】：

let fetchRequest = NSFetchRequest(entityName: “Employee”)

let predicate = NSPredicate(format:”officeId=%@”, "BUI001")

fetchRequest.predicate = predicate

if let fetchResults = try? self.managedObjectContext.executeFetchRequest(fetchRequest)
{
    if fetchResults.count > 0 {
        for bEntity in fetchResults {

            let employeeEntity =  bEntity as! EmployeeEntity                                       
            // append the details to the employeeDetails

    } else
    {
        print(“Details Not Added")
    }
}
return employeeDetails

【讨论】：

请记得解释为什么你的答案能解决问题:)