CoreData/数据存储管理, CoreDataRelationships/关系型数据结构存储管理 的使用

1. CoreData 数据的增删改查操作

  1.1 创建数据实体管理文件

    点击菜单栏 File -> New -> File... -> Core Data 栏下，选择 Data Mode，创建 FruitsContainer.xcdatamodeld 文件

  1.2 创建 FruitEntity 实体表

    打开 FruitsContainer.xcdatamodeld 文件，点击 Add Entity，创建 FruitEntity 实体表，添加 name 属性

  1.3 添加信息如下图:

  1.4 实现

import CoreData
 
// View  - UI
// Model - data point
// ViewModel - manages the data for a view
 
class CoreDataViewModel: ObservableObject{
    // 添加数据容器
    let container: NSPersistentContainer
    // 实体数组
    @Published var savedEntities:[FruitEntity] = []
    
    init() {
        self.container = NSPersistentContainer(name: "FruitsContainer")
        // 加载持久
        self.container.loadPersistentStores { description, error in
            if let error = error{
                print("Error loading core data. \(error)")
            }
        }
        // 获取实体数据
        fetchFruits()
    }
    
    // 获取数据
    func fetchFruits(){
        // 获取实体
        let request = NSFetchRequest<FruitEntity>(entityName: "FruitEntity")
        do {
            savedEntities = try container.viewContext.fetch(request)
        }catch let error{
            print("Error retching. \(error)")
        }
    }
    
    // 添加数据
    func addFruit(text: String){
        let newFruit = FruitEntity(context: container.viewContext)
        newFruit.name = text
        saveData()
    }
    
    // 删除数据
    func deleteFruit(indexSet: IndexSet){
        guard let index = indexSet.first else{ return }
        let fruitEntity = savedEntities[index]
        container.viewContext.delete(fruitEntity)
        saveData()
    }
    
    // 更新数据
    func updateFruit(entity: FruitEntity){
        //let currentName = entity.name ?? ""
        //let newName = currentName + "!"
        //entity.name = newName
        entity.name = (entity.name ?? "").appending("!")
        saveData()
    }
 
    // 保存数据
    func saveData(){
        do{
            try container.viewContext.save()
            fetchFruits()
        }catch let error{
            print("Error saving. \(error)")
        }
    }
}
 
/// 核心数据的使用，新建项目 CoreDataBootcamp 实现修改 Demo 示例
struct CoreDataBootcamp: View {
    @StateObject var vm  = CoreDataViewModel()
    @State var textFileText = ""
    
    var body: some View {
        NavigationView {
            VStack(spacing: 20) {
                TextField("Add fruit here...", text: $textFileText)
                    .font(.headline)
                    .padding(.horizontal)
                    .frame(height: 55)
                    .background(Color.secondary.opacity(0.3))
                    .cornerRadius(10)
                    .padding(.horizontal)
                Button {
                    // 判断是否为空
                    guard !textFileText.isEmpty else { return }
                    vm.addFruit(text: textFileText)
                    textFileText = ""
                } label: {
                    Text("Submit")
                        .font(.headline)
                        .foregroundColor(.white)
                        .frame(height: 55)
                        .frame(maxWidth: .infinity)
                        .background(Color.pink)
                        .cornerRadius(10)
                        .padding(.horizontal)
                }
                List {
                    ForEach(vm.savedEntities) { entity in
                        Text(entity.name ?? "NO Name")
                            .onTapGesture {
                                vm.updateFruit(entity: entity)
                            }
                    }
                    .onDelete(perform: vm.deleteFruit)
                }
                .listStyle(.plain)
            }
            .navigationTitle("Fruits")
        }
    }
}

  1.5 效果图:

2. CoreDataRelationships 关系型数据表结构的操作

  2.1 创建管理数据表文件 CoreDataContainer.xcdatamodeld，实体类，属性及对应关系

  2.2 实体关系表如图:

            

  2.3 实现

import CoreData
 
// 3 enitites
// BusinessEntity 企业
// DepartmentEntity 部门
// EmployeeEntity 员工
 
/// 核心数据操作管理
class CoreDataManager{
    // Sinstance 单例模式
    static let instance = CoreDataManager()
    
    let container: NSPersistentContainer
    let context: NSManagedObjectContext
    
 
    init() {
        container = NSPersistentContainer(name: "CoreDataContainer")
        // 加载数据
        container.loadPersistentStores { description, error in
            if let error = error{
                print("Error loading core data: \(error)")
            }
        }
        context = container.viewContext
    }
    
    // 保存
    func save(){
        do{
            try context.save()
            print("Saved successfully!")
        }catch let error{
            print("Error saving core data: \(error.localizedDescription)")
        }
    }
    
}
 
/// ViewModel
class CoreDataRelationshipViewModel: ObservableObject{
    let manager = CoreDataManager.instance
    /// 所有的企业
    @Published var businesses:[BusinessEntity] = []
    /// 所有的部门
    @Published var departments:[DepartmentEntity] = []
    /// 所有的员工
    @Published var employees:[EmployeeEntity] = []
    
    init() {
        getBusinesses()
        getDepartments()
        getEmployees()
    }
    
    /// 获取企业实体
    func getBusinesses(){
        let request = NSFetchRequest<BusinessEntity>(entityName: "BusinessEntity")
        // 排序
        let sort = NSSortDescriptor(keyPath: \BusinessEntity.name, ascending:  true)
        request.sortDescriptors = [sort]
        
        // 过滤
        //let filter = NSPredicate(format: "name == %@", "Apple")
        //request.predicate = filter
        
        do{
            businesses =  try manager.context.fetch(request)
        }catch let error{
            print("Error fatching. \(error.localizedDescription)")
        }
    }
    
    /// 获取部门实体
    func getDepartments(){
        let request = NSFetchRequest<DepartmentEntity>(entityName: "DepartmentEntity")
        do{
            departments =  try manager.context.fetch(request)
        }catch let error{
            print("Error fatching. \(error.localizedDescription)")
        }
    }
    
    /// 获取所有的员工信息 EmployeeEntity
    func getEmployees(){
        let request = NSFetchRequest<EmployeeEntity>(entityName: "EmployeeEntity")
        do{
            employees = try manager.context.fetch(request)
        }catch let error{
            print("Error fatching. \(error.localizedDescription)")
        }
    }
    
    //获取指定企业的员工
    func getEmployees(forBusiness business: BusinessEntity){
        let request = NSFetchRequest<EmployeeEntity>(entityName: "EmployeeEntity")
        //过滤器
        let filter = NSPredicate(format: "business == %@", business)
        request.predicate = filter
        
        do{
            employees = try manager.context.fetch(request)
        }catch let error{
            print("Error fatching. \(error.localizedDescription)")
        }
    }
    
    /// 更新企业里信息
    func updateBusiness(){
        let existingBusiness = businesses[1]
        existingBusiness.addToDepartments(departments[0])
        // existingBusiness.removeFromDepartments(departments[0])
        // existingBusiness.addToEmployees(employees[0])
        save()
    }
    
    /// 添加企业实体
    func addBusiness(){
        let newBusiness = BusinessEntity(context: manager.context)
        // Apple Microsoft Facebook
        newBusiness.name = "Apple"
        
        // add existing departments to the new business
        // 添加现有的部门实体到新的企业实体内
        // newBusiness.departments = [departments[0], departments[1]]
        
        // add existing employees to the new business
        // 添加现有的员工实体到现的企业实体内
        // newBusiness.employees = [employees[1]]
        
        // add new business to existing department
        // 添加新的企业实体到部门实体内
        // newBusiness.addToDepartments()
        
        // add new business to existing employee
        // 添加新的企业实体到现有的员工实体内
        // newBusiness.addToEmployees()
        save()
    }
    
    /// 添加部门实体
    func addDepartment(){
        let newDepartment = DepartmentEntity(context: manager.context)
        //Marketing Engineering Finance
        newDepartment.name = "Marketing"
        // 对应第一个企业
        newDepartment.businesses = [businesses[0],businesses[1],businesses[2]]
        //newDepartment.addToEmployees(employees[0])
        //newDepartment.employees = [employees[1]]
        //newDepartment.addToEmployees(employees[1])
        save()
    }
   
    /// 添加员工
    func addEmployee(){
        let newEmployee = EmployeeEntity(context: manager.context)
        // Emily John
        newEmployee.name = "John"
        newEmployee.age = 21
        newEmployee.dateJoined = Date()
        
        // 对应企业
        newEmployee.business = businesses[2]
        // 对应部门
        newEmployee.department = departments[1]
        save()
    }
    
    /// 删除部门实体
    func deleteDepartment() {
        let index = 1
        guard departments.count > index else { return }
        let department = departments[index]
        manager.context.delete(department)
        save()
    }
    
    /// 保存
    func save(){
        // 移除数组内容
        businesses.removeAll()
        departments.removeAll()
        employees.removeAll()
        
        // 保存获取数据
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
            self.manager.save()
            self.getBusinesses()
            self.getDepartments()
            self.getEmployees()
        }
    }
}
 
// 核心数据关系型结构
struct CoreDataRelationshipsBootcamp: View {
    // ViewModel
    @StateObject var viewModel = CoreDataRelationshipViewModel()
    
    var body: some View {
        NavigationView {
            ScrollView {
                VStack(spacing: 20) {
                    Button {
                        //viewModel.addBusiness()
                        //viewModel.addDepartment()
                        //viewModel.addEmployee()
                        //viewModel.updateBusiness()
                        viewModel.deleteDepartment()
                    } label: {
                        Text("Perform Action")
                            .foregroundColor(.white)
                            .frame(height: 55)
                            .frame(maxWidth:.infinity )
                            .background(Color.accentColor.cornerRadius(10))
                    }
                    // 企业
                    ScrollView(.horizontal, showsIndicators: true) {
                        HStack(alignment: .top) {
                            ForEach(viewModel.businesses) { business in
                                BusinessView(entity: business)
                            }
                        }
                    }
                    // 部门
                    ScrollView(.horizontal, showsIndicators: true) {
                        HStack(alignment: .top) {
                            ForEach(viewModel.departments) { department in
                                DepartmentView(entity: department)
                            }
                        }
                    }
                    // 员工
                    ScrollView(.horizontal, showsIndicators: true) {
                        HStack(alignment: .top) {
                            ForEach(viewModel.employees) { employee in
                                EmployeeView(entity: employee)
                            }
                        }
                    }
                }
                .padding()
            }
            .navigationTitle("Relationships")
        }
    }
}
 
// 企业视图
struct BusinessView: View{
    let entity: BusinessEntity
    
    var body: some View {
        VStack(alignment: .leading, spacing: 20) {
            Text("Name: \(entity.name ?? "")")
                .bold()
            // 获取企业下的部门
            if let departments = entity.departments?.allObjects as? [DepartmentEntity]{
                Text("Departments:")
                    .bold()
                // 获取所有部门
                ForEach(departments) { department in
                    Text(department.name ?? "")
                }
            }
            
            // 获取企业下的员工
            if let employees = entity.employees?.allObjects as? [EmployeeEntity]{
                Text("Employees:")
                    .bold()
                // 获取所有的员工
                ForEach(employees) { employee in
                    Text(employee.name ?? "")
                }
            }
        }
        .padding()
        .frame(maxWidth: 300,alignment: .leading)
        .background(Color.gray.opacity(0.5))
        .cornerRadius(10)
        .shadow(radius: 10)
    }
}
 
// 部门视图
struct DepartmentView: View{
    let entity: DepartmentEntity
    
    var body: some View {
        VStack(alignment: .leading, spacing: 20) {
            Text("Name: \(entity.name ?? "")")
                .bold()
            // 获取部门的企业
            if let businesses = entity.businesses?.allObjects as? [BusinessEntity]{
                Text("Businesses:")
                    .bold()
                // 获取所有企业
                ForEach(businesses) { business in
                    Text(business.name ?? "")
                }
            }
            
            // 获取部门下的员工
            if let employees = entity.employees?.allObjects as? [EmployeeEntity]{
                Text("Employees:")
                    .bold()
                // 获取所有的员工
                ForEach(employees) { employee in
                    Text(employee.name ?? "")
                }
            }
        }
        .padding()
        .frame(maxWidth: 300,alignment: .leading)
        .background(Color.green.opacity(0.5))
        .cornerRadius(10)
        .shadow(radius: 10)
    }
}
 
// 员工视图
struct EmployeeView: View{
    let entity: EmployeeEntity
    
    var body: some View {
        VStack(alignment: .leading, spacing: 20) {
            Text("Name: \(entity.name ?? "")")
                .bold()
            Text("Age: \(entity.age)")
            Text("Date jiined: \(entity.dateJoined ?? Date())")
            
            // 获取企业
            Text("Businesses:")
                .bold()
            Text(entity.business?.name ?? "")
            
            // 获取部门
            Text("Departmentes:")
                .bold()
            Text(entity.department?.name ?? "")
        }
        .padding()
        .frame(maxWidth: 300,alignment: .leading)
        .background(Color.blue.opacity(0.5))
        .cornerRadius(10)
        .shadow(radius: 10)
    }
}

  2.4 效果图: