如何来设计这个抽象类,我们可以根据oo(面向对象)的思想先来分析一下有哪些对象,这有对象又有哪些行为.
对象:
①管理者,manager类,为了线程安全,这个变量应该是全局的.
②表,Entity对象
行为:
①创建数据库,不需暴露,创建一次就可以
②增加数据,需暴露的接口
③删除数据,需暴露的接口
④修改数据,需暴露的接口
⑤查询数据,需暴露的接口
一 实例化manager类:
static CoreDataManager *_manager;
+ (instancetype)shareManager
{
return [[self alloc] init];
}
+ (instancetype)allocWithZone:(struct _NSZone *)zone
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_manager = [super allocWithZone:zone];
});
return _manager;
NSManagedObjectContext:An object representing a single object space or scratch pad that you use to fetch, create, and save managed objects.
官方文档的意思是需要通过这个上下文对象来进行对coredata的增删改查操作.
所以manger就需要拥有Context这个属性
@interface CoreDataManager()
@property (nonatomic , strong)NSManagedObjectContext *context;
@end
通过懒加载的方式来实例化content,并创建数据库
- (NSManagedObjectContext *)context
{
if (!_context) {
//1.经过编译后数据模型文件的扩展名由xcdatamodeld变成了momd
NSURL *modelUrl = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
//2.构建CoreData的模型文件
NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelUrl];
//3.通过模型文件创建PersistentStoreCoordinator对象
NSPersistentStoreCoordinator *coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
//4.数据库存储路径URL
NSURL *dbUrl = [NSURL fileURLWithPath:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject stringByAppendingPathComponent:@"test.sqlite"]];
//5.设置persistStore的持久化存储方式为SQLiteStoreType,代表persistStore会自动生成一个SQLite数据库文件来实现持久化存储，并会自动生成SQL语句来做CRUD（增删改查)
/***************************************************数据库升级*****************************************************************************/
NSDictionary *optionsDictionary = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],
NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES],NSInferMappingModelAutomaticallyOption, nil];
if (![coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:dbUrl options:optionsDictionary error:nil]) {
NSLog(@"failed to add persistent store with type to persistent store coordinator");
}
/****************************************************************************************************************************************/
//6.NSManagedObjectContext:所有的ManagedObject的增删改查都是在context上进行的。
//NSMainQueueConcurrencyType:这个context所关联的控制器和UI控件只能在主线程中使用
_context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
_context.persistentStoreCoordinator = coordinator;
return _context;
}
二 提供增删改查的接口的内部实现
//MARK: -
//MARK: --插入数据
- (void)insertParameter:(NSDictionary *)parameter tableName:(NSString *)tableName
{
NSManagedObject *obj = [NSEntityDescription insertNewObjectForEntityForName:tableName inManagedObjectContext:self.context];
for (NSString *key in parameter.allKeys) {
[obj setValue:parameter[key] forKey:key];
}
if ([self.context save:nil]) {
NSLog(@"save success");
}else{
NSLog(@"save failure");
}
}
//MARK: -
//MARK: --删除
- (void)deleteDataWithTableName:(NSString *)tableName predicate:(NSPredicate *)predicate
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:tableName];
request.predicate = predicate;
NSArray *results = [self.context executeFetchRequest:request error:nil];
for (NSManagedObject *obj in results) {
[self.context deleteObject:obj];
}
if ([self.context save:nil]) {
NSLog(@"save success");
}else{
NSLog(@"save failure");
}
}
//MARK: -
//MARK: -- 更新数据
- (void)updateWithAttribute:(id)attribute key:(NSString *)key tableName:(NSString *)tableName predicate:(NSString *)predicateString
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:tableName];
NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateString];
request.predicate = predicate;
NSArray *results = [self.context executeFetchRequest:request error:nil];
for (NSManagedObject *obj in results) {
[obj setValue:attribute forKey:key];
}
//保存
if ([self.context save:nil]) {
NSLog(@"operate success");
}else{
NSLog(@"operate failed");
}
}
//MARK: -
//MARK: --查询数据
- (NSArray *)selectWithTableName:(NSString *)tableName predicate:(NSString *)predicateString
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:tableName];
NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateString];
request.predicate = predicate;
NSArray *results = [self.context executeFetchRequest:request error:nil];
return results;
}
三 导入coredata文件并进行设置
四 增删改查
//MARK: -
//MARK: --增
- (IBAction)add:(id)sender {
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:1],
@"name" : @"AAA",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:2],
@"name" : @"BBB",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:3],
@"name" : @"CCC",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:4],
@"name" : @"DDD",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:5],
@"name" : @"EEE",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:6],
@"name" : @"FFF",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:7],
@"name" : @"GGG",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:8],
@"name" : @"HHH",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:9],
@"name" : @"III",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:10],
@"name" : @"JJJ",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:11],
@"name" : @"KKK",
} tableName:Table_People];
[Manager insertParameter:@{
@"age" : [NSNumber numberWithInt:12],
@"name" : @"LLL",
} tableName:Table_People];
}
//MARK: -
//MARK: --删
- (IBAction)delete:(id)sender {
[Manager deleteDataWithTableName:Table_People predicate:@"age=1"];
}
//MARK: -
//MARK: --改
- (IBAction)update:(id)sender {
[Manager updateWithAttribute:@"KimmyKing" key:@"name" tableName:Table_People predicate:@"name='BBB'"];
}
//MARK: -
//MARK: --查
- (IBAction)select:(id)sender {
NSArray *arr = [Manager selectWithTableName:Table_People predicate:@"age>10"];
for (People *p in arr) {
NSLog(@"%@今年%@岁了",p.name,p.age);
}
}
五 数据库升级
当数据库需要增加或修改字段时,原有的数据库就不能使用了,需要使用新的数据库
