CoreData 基础

创建时
1. 基本原理图

2. 创建

AppDelegate

#pragma mark - Core Data stack
// 被管理对象上下文(数据管理器)
相当于一个临时数据库
@synthesize managedObjectContext =
_managedObjectContext;
// 被管理对象模型(数据模型器)
@synthesize managedObjectModel =
_managedObjectModel;
// 持久化存储助理(数据连接器)
整个 coredata 框架的核心
@synthesize persistentStoreCoordinator =
_persistentStoreCoordinator;

// 获取真实文件的存储路径
- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "com.hk.CoreData" in the application's documents directory.
return [[[NSFileManager
defaultManager] URLsForDirectory:NSDocumentDirectory
inDomains:NSUserDomainMask]
lastObject];
}

- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel !=
nil) {
return
_managedObjectModel;
}
NSURL *modelURL = [[NSBundle
mainBundle] URLForResource:@"CoreData"
withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel
alloc] initWithContentsOfURL:modelURL];
return
_managedObjectModel;
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator !=
nil) {
return
_persistentStoreCoordinator;
}

// Create the coordinator and store

_persistentStoreCoordinator = [[NSPersistentStoreCoordinator
alloc] initWithManagedObjectModel:[self
managedObjectModel]];
NSURL *storeURL = [[self
applicationDocumentsDirectory]
URLByAppendingPathComponent:@"CoreData.sqlite"];
NSError *error =
nil;
NSString *failureReason =
@"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator
addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:storeURL options:nil
error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary
dictionary];
dict[NSLocalizedDescriptionKey] =
@"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSError
errorWithDomain:@"YOUR_ERROR_DOMAIN"
code:9999
userInfo:dict];
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error
userInfo]);
abort();
}

return
_persistentStoreCoordinator;
}

- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext !=
nil) {
return
_managedObjectContext;
}

NSPersistentStoreCoordinator *coordinator = [self
persistentStoreCoordinator];
if (!coordinator) {
return
nil;
}
_managedObjectContext = [[NSManagedObjectContext
alloc] init];
[_managedObjectContext
setPersistentStoreCoordinator:coordinator];
return
_managedObjectContext;
}

#pragma mark - Core Data Saving support
// 把我们临时数据库中进行的改变进行永久保存
- (void)saveContext {
NSManagedObjectContext *managedObjectContext =
self.managedObjectContext;
if (managedObjectContext !=
nil) {
NSError *error =
nil;
if ([managedObjectContext
hasChanges] && ![managedObjectContext
save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error
userInfo]);
abort();
}
}
}

ViewController
#import "ViewController.h"
#import "AppDelegate.h"
#import "Cloths.h"

@interface ViewController () <UITableViewDataSource,UITableViewDelegate>
@property (strong,
nonatomic) IBOutlet
UITableView *tableView;

@property (nonatomic,
strong) NSMutableArray *dataArray;

// 声明一个 AppDelegate
对象属性, 用来调用类中的属性,
比如管理对象上下文
@property (nonatomic,
strong) AppDelegate *myAppDelegate;

@end

@implementation ViewController

- (void)viewDidLoad {
[super
viewDidLoad];

self.dataArray = [NSMutableArray
array];
self.myAppDelegate = [UIApplication
sharedApplication].delegate;

// 查询数据
// 1. NSFetchResqust对象
NSFetchRequest *request = [[NSFetchRequest
alloc]initWithEntityName:@"Cloths"];
// 2. 设置排序
// 2.1 创建排序描述对象(根据模型中的属性排序)
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor
alloc]initWithKey:@"price"
ascending:YES];
request.sortDescriptors =
@[sortDescriptor];

// 执行这个查询
// 捕捉 error
信息
NSError *error =
nil;
NSArray *resultArray = [self.myAppDelegate.managedObjectContext
executeFetchRequest:request
error: &error];

// 给数据源数组添加数据
[self.dataArray
addObjectsFromArray:resultArray];

}

// 插入数据 (tabbar
点击事件)
- (IBAction)addModel:(id)sender
{
// 插入数据
// 创建实体描述对象
NSEntityDescription *description = [NSEntityDescription
entityForName:@"Cloths"
inManagedObjectContext:self.myAppDelegate.managedObjectContext];

// 1. 先创建一个模型对象
Cloths *cloth = [[Cloths
alloc]initWithEntity: description
insertIntoManagedObjectContext:self.myAppDelegate.managedObjectContext];
// 属性赋值
cloth.name =
@"Puma";
int price =
arc4random() % 1000 +
1;
cloth.price = [NSNumber
numberWithInt:price];

// 插入数据源数组
[self.dataArray
addObject:cloth];

// 插入 UI
[self.tableView
insertRowsAtIndexPaths:@[[NSIndexPath
indexPathForRow:self.dataArray.count -
1 inSection:0]]
withRowAnimation:UITableViewRowAnimationLeft];

// 对数据管理器中的更改进行永久存储
[self.myAppDelegate
saveContext];
}

// 返回多少行
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return
self.dataArray.count;
}

// cell的设置
- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath
*)indexPath
{
UITableViewCell *cell = [tableView
dequeueReusableCellWithIdentifier:@"cell"
forIndexPath:indexPath];

Cloths *cloth =
self.dataArray[indexPath.row];
cell.textLabel.text = [NSString
stringWithFormat:@"%@ -- %@", cloth.name, cloth.price];

return cell;
}

// 允许 table可以编辑
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
return
YES;
}

// 删除数据
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle ==
UITableViewCellEditingStyleDelete) {
// 先取出数据
Cloths *cloth =
self.dataArray[indexPath.row];
// 删除数据源
[self.dataArray
removeObject:cloth];
// 删除数据管理器中的数据
[self.myAppDelegate.managedObjectContext
deleteObject:cloth];
// 将进行的更改进行永久保存
[self.myAppDelegate
saveContext];
// 删除单元格
[self.tableView
deleteRowsAtIndexPaths:@[indexPath]
withRowAnimation:UITableViewRowAnimationFade];
}
}

// cell 点击方式
修改数据
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// 1. 找到模型对象
Cloths *cloth =
self.dataArray[indexPath.row];
cloth.name =
@"Nick";

// 刷新单元行
[self.tableView
reloadRowsAtIndexPaths:@[indexPath]
withRowAnimation:UITableViewRowAnimationFade];

// 永久保存更改数据 saveContext方法
[self.myAppDelegate
saveContext];
}