iOS: Core Data入门-白红宇

iOS: Core Data入门

阅读量：6261 次

发布时间：2019-06-22

本文共 7456 字，大约阅读时间需要 24 分钟。

Core Data是ORM框架，很像.NET框架中的EntityFramework。使用的基本步骤是：

在项目属性里引入CoreData.framework (标准库)

在项目中新建DataModel (生成*.xcdatamodeld文件)

在DataModel里创建Entity

为Entity生成头文件(菜单Editor/Create NSMangedObject Subclass...)

在项目唯一的委托类(AppDelegate.h, AppDelegate.m)里添加managedObjectContext 用来操作Core Data

代码任意位置引用 managedObjectContext 读写数据

模型：（注意：myChapter, myContent这些关系都是Cascade,这样删父对象时才会删除子对象）

生成的头文件：

/* Book.h */@interface Book : NSManagedObject@property (nonatomic, retain) NSNumber * bookId;@property (nonatomic, retain) NSString * name;@property (nonatomic, retain) NSString * author;@property (nonatomic, retain) NSString * summary;@property (nonatomic, retain) NSSet *myChapters;@end@interface Book (CoreDataGeneratedAccessors)- (void)addMyChaptersObject:(NSManagedObject *)value;- (void)removeMyChaptersObject:(NSManagedObject *)value;- (void)addMyChapters:(NSSet *)values;- (void)removeMyChapters:(NSSet *)values;@end/* Chapter.h */@class Book;@interface Chapter : NSManagedObject@property (nonatomic, retain) NSNumber * chapId;@property (nonatomic, retain) NSString * name;@property (nonatomic, retain) NSNumber * orderId;@property (nonatomic, retain) Book *ownerBook;@property (nonatomic, retain) NSManagedObject *myContent;@end/* TextContent.h */@class Chapter;@interface TextContent : NSManagedObject@property (nonatomic, retain) NSNumber * chapId;@property (nonatomic, retain) NSString * text;@property (nonatomic, retain) Chapter *ownerChapter;@end

委托类代码

AppDelegate.h

// AppDelegate.h#import 
     
      #import 
      
       #import "Book.h"#import "Chapter.h"#import "TextContent.h"@interface AppDelegate : UIResponder 
       
        @property (strong, nonatomic) UIWindow *window;@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;@end

AppDelegate.m

@implementation AppDelegate@synthesize managedObjectContext = _managedObjectContext;-(NSManagedObjectContext *)managedObjectContext{    if (_managedObjectContext != nil) {        return _managedObjectContext;    }        _managedObjectContext = [[NSManagedObjectContext alloc]init];        // 设置数据库路径    NSURL *url = [[[NSFileManager defaultManager]                   URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask]lastObject];    NSURL *storeDataBaseURL = [url URLByAppendingPathComponent:@"BOOKS.sqlite"];        // 创建presistentStoreCoordinator    NSError *error = nil;    NSPersistentStoreCoordinator *presistentStoreCoordinator  = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[NSManagedObjectModel mergedModelFromBundles: nil]];        // 指定存储类型和路径    if (![presistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType                configuration:nil URL:storeDataBaseURL options:nil error:&error]) {        NSLog(@"error : %@", error);    }        [_managedObjectContext setPersistentStoreCoordinator: presistentStoreCoordinator];    return _managedObjectContext;}

使用_managedObjectContext操作Core Data

// 保存新对象-(void) testStore{    // 从AppDelegate 获得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];    // 第一个章节    TextContent *content1 = [NSEntityDescription insertNewObjectForEntityForName:@"TextContent" inManagedObjectContext:context];    content1.chapId = [NSNumber numberWithInt:100];    content1.text = @"hello1";        Chapter *chapter1 = (Chapter *)[NSEntityDescription insertNewObjectForEntityForName:@"Chapter" inManagedObjectContext:context];    chapter1.name = @"hello1";    chapter1.orderId = [NSNumber numberWithInt:0];    chapter1.chapId =  [NSNumber numberWithInt:100];    chapter1.myContent = content1;        // 第二个章节    TextContent *content2 = [NSEntityDescription insertNewObjectForEntityForName:@"TextContent" inManagedObjectContext:context];    content2.chapId = [NSNumber numberWithInt:100];    content2.text = @"hello2";        Chapter *chapter2 = (Chapter *)[NSEntityDescription insertNewObjectForEntityForName:@"Chapter" inManagedObjectContext:context];    chapter2.name = @"hello2";    chapter2.orderId = [NSNumber numberWithInt:1];    chapter2.chapId =  [NSNumber numberWithInt:101];    chapter2.myContent = content2;        // 书籍对象    Book *book = (Book *)[NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:context];    book.bookId = [NSNumber numberWithInt:100];    book.name = @"hello";    book.author = @"Kitty";    book.summary = @"test";    [book addMyChaptersObject:chapter1];    [book addMyChaptersObject:chapter2];        // 提交到持久存储    if ([context hasChanges]) {        [context save:nil];    }}// 读取对象-(void) testRead{    // 从AppDelegate 获得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 生成查询对象 （查询全部数据）    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 执行查询    NSError *error;    NSArray *arrayBooks = [context executeFetchRequest:request error:&error];    // 定义排序方式 （根据集合中Chapter对象的orderId属性排序，升序）    NSSortDescriptor *chaptersDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"orderId" ascending:YES];        // 遍历结果集    for (Book *book in arrayBooks) {                // 使用当前对象属性        NSLog(@"book name = %@", book.name);                // 使用当前对象的集合属性，转成数组        NSArray *arrayChapters = [book.myChapters allObjects];                // 排序        arrayChapters = [arrayChapters                          sortedArrayUsingDescriptors:[NSArray arrayWithObjects:chaptersDescriptor,nil]];                // 遍历子数组        for (Chapter *chapter in arrayChapters) {            NSLog(@"chapter name = %@", chapter.name);                        TextContent *content = (TextContent*) chapter.myContent;            NSLog(@"chapter text = %@", content.text);        }    }}// 更新对象属性-(void) testUpdate{    // 从AppDelegate 获得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 生成Request对象    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 执行查询    NSError *error;    NSArray *array = [context executeFetchRequest:request error:&error];        // 更改对象属性    Book * book = array[0];    book.name = @"BOOKS";        // 提交到持久存储    if ([context hasChanges]) {        [context save:nil];    }}// 删除对象-(void) testRemove{    // 从AppDelegate 获得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 生成Request对象    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 执行查询    NSError *error;    NSArray *array = [context executeFetchRequest:request error:&error];        // 遍历删除对象,因为在模型里把关系设置为Cascade,所以子对象会被自动删除    for (Book *book in array) {        [context deleteObject:book];    }        // 提交到持久存储    if ([context hasChanges]) {        [context save:nil];    }}

转载于:https://www.cnblogs.com/code-style/p/4016390.html

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