2020-02-17-Demo之iOS使用CoreData

Demo之iOS使用CoreData

准备

Xcode 添加 Coredata.framework 依赖库
确认是否存在 xxxCoreData.xcdatamodeld , 没有就新建一个, 在AppDelegate里可能会新出现一些代码
打开 xxxCoreData.xcdatamodeld 确认以下
ENTITIES里添加xxxEntity(也就是类obj),并添加属性及属性类型
CONFIGURATIONS里确认Entity及Class是否存在上一行的那个xxxEntity,其abstract不勾选(Demo用不上)

代码

#import <CoreData/CoreData.h>
#import "AppDelegate.h"
#import "xxxCoreData+CoreDataModel.h"
#import "xxxEntity+CoreDataClass.h"
#import "xxxEntity+CoreDataProperties.h"
<UIApplicationDelegate>
@property (retain, strong) NSPersistentContainer *persistentContainer;
/** NSManagedObjectContext */
@property(nonatomic, strong)NSManagedObjectContext *managedObjectContext;
- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self initCoreData];
    [self insert];
    [self tapSearchBtn];
}
// 懒加载
- (NSManagedObjectContext *)managedObjectContext {
    // 因为在AppDelegate中已经实现过了，所以在这里是从AppDelegate中去获取
    if (!_managedObjectContext) {
        // 获取appDelegate对象
        AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
        _managedObjectContext = appDelegate.persistentContainer.viewContext;
    }
    return _managedObjectContext;
}
-(void)initCoreData {
    NSError *error;         //Path to sqlite file.
    NSString *path = [NSHomeDirectory() stringByAppendingString:@"/Documents/xxxEntity.sqlite"];
    NSURL *url = [NSURL fileURLWithPath:path];          //init the model
    NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];          //Establish the persistent store coordinator
    NSPersistentStoreCoordinator *persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
    if(![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error])
    {
        NSLog(@"Error %@",[error localizedDescription]);
    }else{
        self.managedObjectContext = [[NSManagedObjectContext alloc ] initWithConcurrencyType:NSMainQueueConcurrencyType];
        [self.managedObjectContext setPersistentStoreCoordinator:persistentStoreCoordinator];
    }
}
- (xxxEntity *)insert {
    NSError *error = nil;
    if (self.managedObjectContext == nil) {     NSLog(@"managedObjectContext is nil");     return nil; }
    xxxEntity * hfile = [NSEntityDescription insertNewObjectForEntityForName:@"xxxEntity" inManagedObjectContext:self.managedObjectContext];
    hfile.fileversion = @"version1";
    hfile.filename = [NSString stringWithFormat:@"%u", arc4random() % 1000];
    hfile.filepath = @"path1";
    if ([self.managedObjectContext hasChanges] && ![self.managedObjectContext save:&error]) {
        NSLog(@"Unresolved error %@, %@", error, error.userInfo);
        return nil;
    } else {
        NSLog(@"Unresolved error %@", @"插入数据成功");
    }
    return hfile;
}
- (NSArray *)search {
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"xxxEntity"];
    // 执行获取操作，获取所有Student托管对象
    NSError *error = nil;
    NSArray<xxxEntity *> *hfileArray = [self.managedObjectContext executeFetchRequest:request error:&error];
    if (error) {
        NSLog(@"%@", [NSString stringWithFormat:@"CoreData Error:%@",error.description]);
    } else {
        NSLog(@"查找数据成功 %@", NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES));
        for (xxxEntity *hfile in hfileArray) {
            NSLog(@"%@ %@ %@", hfile.fileversion, hfile.filename, hfile.filepath);
        }
    }
    return hfileArray;
}
// 获取数据的请求对象，指明对实体进行查询操作
- (void)tapSearchBtn {
    NSArray *sts = [self search];
    if (sts.count == 0) {
        return;
    }
    // 遍历
    //[self.dataSources removeAllObjects];
    [sts enumerateObjectsUsingBlock:^(xxxEntity * obj, NSUInteger idx, BOOL *stop) {
        //[self.dataSources addObject:obj];
        NSLog(@"%@", obj);
    }];
    //[self.tableView reloadData];
}

以下代码是xcode直接生成在AppDelegate里的,不需要重复添加,列在这里只是备个份

#pragma mark - Core Data stack

@synthesize persistentContainer = _persistentContainer;

- (NSPersistentContainer *)persistentContainer {
    // The persistent container for the application. This implementation creates and returns a container, having loaded the store for the application to it.
    @synchronized (self) {
        if (_persistentContainer == nil) {
            _persistentContainer = [[NSPersistentContainer alloc] initWithName:@"xxxCoreData"];
            [_persistentContainer loadPersistentStoresWithCompletionHandler:^(NSPersistentStoreDescription *storeDescription, NSError *error) {
                if (error != nil) {
                    // 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.

                    /*
                     Typical reasons for an error here include:
                     * The parent directory does not exist, cannot be created, or disallows writing.
                     * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                     * The device is out of space.
                     * The store could not be migrated to the current model version.
                     Check the error message to determine what the actual problem was.
                    */
                    NSLog(@"Unresolved error %@, %@", error, error.userInfo);
                    abort();
                }
            }];
        }
    }

    return _persistentContainer;
}

#pragma mark - Core Data Saving support

- (void)saveContext {
    NSManagedObjectContext *context = self.persistentContainer.viewContext;
    NSError *error = nil;
    if ([context hasChanges] && ![context 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();
    }
}