CoreData的简单使用<四、多个数据库>

CoreData的多个数据库

CoreData的多个数据库，每一个数据库需要对应一个上下文。

////  ViewController.m//  CoreData////  Created by YanFengZheng on 16/8/27.//  Copyright © 2016年 fe. All rights reserved.//#import "ViewController.h"#import <CoreData/CoreData.h>#import "Employee.h"#import "Friendster.h"@interface ViewController ()@property (nonatomic,strong) NSManagedObjectContext *componyContext;@property (nonatomic,strong) NSManagedObjectContext *weiChartContext;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    self.componyContext = [self getContextWithDateModel:@"Compony.momd"];    self.weiChartContext = [self getContextWithDateModel:@"WeiChart.momd"];}#pragma mark - 数据库操作 增、删、改、查//1.插入数据- (IBAction)insertData:(UIButton *)sender {    //插入数据的时候，需要使用实体描述拿到实体模型    Employee *employee = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.componyContext];    employee.name = @"王五";    employee.height = @190;    employee.birthday = [NSDate date];        [self.componyContext  save:nil];        Friendster *friend = [NSEntityDescription insertNewObjectForEntityForName:@"Friendster" inManagedObjectContext:self.weiChartContext];    friend.text = @"秋天来了，天气凉了";    friend.date = [NSDate date];    [self.weiChartContext  save:nil];}//查询员工- (IBAction)queryData:(UIButton *)sender {    //1:FectchRequest 抓取请求对象    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];    //2:设置过滤条件    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name = %@",@"王五"];    request.predicate = pre;    //3:设置排序    NSSortDescriptor *height = [NSSortDescriptor sortDescriptorWithKey:@"height" ascending:YES];    request.sortDescriptors = @[height];        //4:执行请求    NSArray *emps = [self.componyContext executeFetchRequest:request error:nil];    //遍历查询结果    for (Employee *emp in emps) {        NSLog(@"名字：%@,身高：%@,生日：%@",emp.name,emp.height,emp.birthday);    }}- (NSManagedObjectContext *)getContextWithDateModel:(NSString *)dataModel{    //1.创建模型文件［相当于数据库里的表］    //2.添加实体   ［一张表］    //3.创建实体类 ［相当于模型］    //4.生成上下文 关联模型文件生成数据库    //4.1上下文    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];    //4.2持久化存储协调器    NSURL *componryURL = [[NSBundle mainBundle] URLForResource:dataModel withExtension:nil];    NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:componryURL];    NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];    //4.3设置数据库路径    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];    NSString *sqliteName = [[dataModel componentsSeparatedByString:@"."] firstObject];    NSString *sqlitePath = [doc stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.sqlite",sqliteName]];    NSLog(@"%@",sqlitePath);    [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:nil];    context.persistentStoreCoordinator = store;    return context;        /*在写以上代码的时候，先初始化上下文，再初始化上下文需要的持久化存储协调器，再初始化持久化存储协调器所需要的模型文件，最后添加持久化类型和文件路径。个人感觉按照这个方法比较容易记忆。     */    }@end