CoreData的使用

Core Data是iOS5之后才出现的一个框架，它提供了对象-关系映射(ORM)的功能，即能够将OC对象转化成数据，保在SQLite数据库文件中，也能够将保存在数据库中的数据还原成OC对象。在此数据操作期间，我们不需要编写任何SQL语句

CoreData的使用步骤

1.创建模型文件相当于数据库

2.添加实体相当表

3.创建实体类相于模型类

4.生成上下文 关联模型文件生成数据库

5.保存对象到数据库

6.从数据库获取对象

7.更新数据

8.删除数据

1、创建模型文件：（相当于数据库）

2、添加实体（相当于表）

3、创建实体类（相当于模型类）

4、生成上下文 关联模型文件生成数据库

<span style="font-size:18px;">// 1.上下文 关联Company.xcdatamodeld 模型文件    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];        // 关联模型文件        // 创建一个模型对象    // 传一个nil 会把 bundle下的所有模型文件 关联起来    NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];        // 创建一个持久化存储调度器    NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];           // 存储数据库的名字    NSError *error = nil;        // 获取docment目录    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];        // 数据库保存的路径（拼接路径）    NSString *sqlitePath = [doc stringByAppendingPathComponent:@"company.sqlite"];        [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:&error];        // 上下文的持久化存储调度器赋值    context.persistentStoreCoordinator = store;        self.context = context;</span><span style="color:#4f81bd;font-size:24px;"></span>

增、删、改、查

增：

#pragma mark 添加员工信息- (IBAction)addEmployee:(id)sender {        // 创建员工    Employee *emp1 = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context];        // 设置员工属性    emp1.name = @"lisi";    emp1.age = @28;    emp1.height = @2.10;        //保存 - 通过上下文操作    NSError *error = nil;    [self.context save:&error];    if (!error) {        NSLog(@"success");    }else{        NSLog(@"%@",error);    }}

查：

#pragma mark 读取员工信息- (IBAction)readEmployee:(id)sender {        //创建一个请求对象 （填入要查询的表名-实体类）    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        // 过滤查询    // 查找张三 并且身高大于1.8//    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@ AND height > %@",@"zhangsan",@(1.8)];//    request.predicate = pre;        //排序 以身高进行升序//    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"height" ascending:NO];//    request.sortDescriptors = @[sort];        // 分页查询 总共13条数据 每页显示5条数据    //第一页的数据    request.fetchLimit = 5;    request.fetchOffset = 10;            //读取信息    NSError *error = nil;    NSArray *emps = [self.context executeFetchRequest:request error:&error];    if (!error) {        NSLog(@"emps: %@",emps);        for (Employee *emp in emps) {            NSLog(@"%@ %@ %@",emp.name,emp.age,emp.height);        }    }else{        NSLog(@"%@",error);    }}

#pragma mark 模糊查询- (IBAction)likeSearcher:(id)sender {        // 查询    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        // 过滤    // 1.查询以wang开头员工    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name BEGINSWITH %@",@"wang"];        // 2.以si 结尾    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name ENDSWITH %@",@"si"];        // 3.名字包含 g    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name CONTAINS %@",@"g"];        // 4.like 以si结尾    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name like %@",@"li*"];    request.predicate = pre;        //读取信息    NSError *error = nil;    NSArray *emps = [self.context executeFetchRequest:request error:&error];    if (!error) {        NSLog(@"emps: %@",emps);        for (Employee *emp in emps) {            NSLog(@"%@ %@ %@",emp.name,emp.age,emp.height);        }    }else{        NSLog(@"%@",error);    }  }

改：

#pragma mark 更新员工信息- (IBAction)updateEmployee:(id)sender {        // 把wangwu的身高更改成 1.7    // 1.查找wangwu    NSArray *emps = [self findEmployeeWithName:@"wangwu"];        // 2.更新身高    if (emps.count == 1) {        Employee *emp = emps[0];        emp.height = @1.7;    }        // 3.同步（保存）到数据    [self.context save:nil];}-(NSArray *)findEmployeeWithName:(NSString *)name{    // 1.查找员工    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name];    request.predicate = pre;            return [self.context executeFetchRequest:request error:nil];    }

删：

#pragma mark 删除员工- (IBAction)deleteEmployee:(id)sender {    [self deleteEmployeeWithName:@"lisi"];}-(void)deleteEmployeeWithName:(NSString *)name{    // 删除zhangsan    // 1.查找到zhangsan    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name];    request.predicate = pre;        // 2.删除zhangsan    NSArray *emps = [self.context executeFetchRequest:request error:nil];        for (Employee *emp in emps) {        NSLog(@"删除员工的人 %@",emp.name);        [self.context deleteObject:emp];    }        // 3.用context同步下数据库    //所有的操作暂时都是在内存里，调用save 同步数据库    [self.context save:nil];}

多表关联：

增删改查：

增：

#pragma mark 添加员工信息- (IBAction)addEmployee:(id)sender {        // 创建员工    // 1.添加zhangsan 属于ios部门    Employee *emp1 = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context];    emp1.name = @"zhangsan";    emp1.height = @1.7;    emp1.age = @27;        // 创建ios部门    Department *dep1 = [NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.context];    dep1.name = @"ios";    dep1.createDate = [NSDate date];    dep1.departNo = @"D001";            emp1.depart = dep1;                // 2.添加lisi 属于android 部门    Employee *emp2 = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context];    emp2.name = @"lisi";    emp2.height = @1.7;    emp2.age = @27;        // 创建android部门    Department *dep2 = [NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.context];    dep2.name = @"android";    dep2.createDate = [NSDate date];    dep2.departNo = @"D002";            emp2.depart = dep2;            //一次保存    [self.context save:nil];    }

查：

#pragma mark 读取员工信息- (IBAction)readEmployee:(id)sender {        //查找ios部门的员工    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        // 过滤查询    NSPredicate *pre = [NSPredicate predicateWithFormat:@"depart.name = %@",@"ios"];    request.predicate = pre;            //读取信息    NSError *error = nil;    NSArray *emps = [self.context executeFetchRequest:request error:&error];    if (!error) {        NSLog(@"emps: %@",emps);        for (Employee *emp in emps) {            NSLog(@"name:%@ departName:%@ ",emp.name,emp.depart.name);        }    }else{        NSLog(@"%@",error);    }}

#pragma mark 模糊查询- (IBAction)likeSearcher:(id)sender {        // 查询    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        // 过滤    // 1.查询以wang开头员工    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name BEGINSWITH %@",@"wang"];        // 2.以si 结尾    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name ENDSWITH %@",@"si"];        // 3.名字包含 g    //NSPredicate *pre = [NSPredicate predicateWithFormat:@"name CONTAINS %@",@"g"];        // 4.like 以si结尾    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name like %@",@"li*"];    request.predicate = pre;        //读取信息    NSError *error = nil;    NSArray *emps = [self.context executeFetchRequest:request error:&error];    if (!error) {        NSLog(@"emps: %@",emps);        for (Employee *emp in emps) {            NSLog(@"%@ %@ %@",emp.name,emp.age,emp.height);        }    }else{        NSLog(@"%@",error);    }  }

改：

#pragma mark 更新员工信息- (IBAction)updateEmployee:(id)sender {        // 把wangwu的身高更改成 1.7    // 1.查找wangwu    NSArray *emps = [self findEmployeeWithName:@"wangwu"];        // 2.更新身高    if (emps.count == 1) {        Employee *emp = emps[0];        emp.height = @1.7;    }        // 3.同步（保存）到数据    [self.context save:nil];}-(NSArray *)findEmployeeWithName:(NSString *)name{    // 1.查找员工    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name];    request.predicate = pre;            return [self.context executeFetchRequest:request error:nil];    }

删：

#pragma mark 删除员工- (IBAction)deleteEmployee:(id)sender {    [self deleteEmployeeWithName:@"lisi"];}-(void)deleteEmployeeWithName:(NSString *)name{    // 删除zhangsan    // 1.查找到zhangsan    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];        NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name];    request.predicate = pre;        // 2.删除zhangsan    NSArray *emps = [self.context executeFetchRequest:request error:nil];        for (Employee *emp in emps) {        NSLog(@"删除员工的人 %@",emp.name);        [self.context deleteObject:emp];    }        // 3.用context同步下数据库    //所有的操作暂时都是在内存里，调用save 同步数据库    [self.context save:nil];}

多个数据库：

     

一个上下文只能关联一个数据库，所以需要创建两个上下文

<span style="font-family: 微软雅黑;">- (void)viewDidLoad {</span>

    [super viewDidLoad];    //创建company上下文    self.companyContext = [self setupContextWithModelName:@"Company"];            //创建weibo上下文    self.weiboContext = [self setupContextWithModelName:@"Weibo"];   }/** *  根据模型文件名 返回上下文 */-(NSManagedObjectContext *)setupContextWithModelName:(NSString *)modelName{        // 1.上下文 关联Company.xcdatamodeld 模型文件    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];        // 关联模型文件        // 创建一个模型对象    // 传一个nil 会把 bundle下的所有模型文件 关联起来    // 查找model文件的URL    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:modelName withExtension:@"momd"];    NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];        // 持久化存储调度器    NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];        // 存储数据库的名字    NSError *error = nil;        // 获取docment目录    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];        // 数据库保存的路径    NSString *sqlitePath = [doc stringByAppendingFormat:@"/%@.slqite",modelName];        [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:&error];        context.persistentStoreCoordinator = store;        return context;}

#pragma mark 添加员工和微博信息信息- (IBAction)addEmployee:(id)sender {    //创建员工    Employee *emp = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.companyContext];    emp.name = @"zhangsan";    emp.height = @1.8;    emp.age = @25;        [self.companyContext save:nil];        //创建微博    Status *sts = [NSEntityDescription insertNewObjectForEntityForName:@"Status" inManagedObjectContext:self.weiboContext];        sts.text = @"祝愿大家找到好工作";    sts.author = @"gzios 1期";    sts.createDate = [NSDate date];    [self.weiboContext save:nil];}

sqlite 和 CoreData 对比

 sqlite是纯c语言存储数据方式

 coredata也是对sqlite的封装，它数据的保存直接使用对象，不用再写sql语句

 sqlite 性能优于 coredata

•什么时候使用sqlite什么时候使用CoreData

 "Coredata功能不是很强大

 如果你的数据库表关联大复杂三四张表都关联 -sqlite

 如果数据表结构比较简单就只有两三张，这些表没有关联关系 coreData