iOS: Core Data入門

標籤：des   style   blog   http   color   io   os   使用   ar   

Core Data是ORM架構，很像.NET架構中的EntityFramework。使用的基本步驟是：

• 在項目屬性裡引入CoreData.framework (標準庫)
• 在項目中建立DataModel (產生*.xcdatamodeld檔案)
• 在DataModel裡建立Entity 
• 為Entity產生標頭檔(菜單Editor/Create NSMangedObject Subclass...)
• 在項目唯一的委託類(AppDelegate.h, AppDelegate.m)裡添加managedObjectContext 用來操作Core Data
• 代碼任意位置引用 managedObjectContext 讀寫資料

模型：（注意：myChapter, myContent這些關係都是Cascade,這樣刪父物件時才會刪除子物件）

產生的標頭檔：

/* 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

 

委託類代碼

 

AppDelegate.h

// AppDelegate.h#import <UIKit/UIKit.h>#import <CoreData/CoreData.h>#import "Book.h"#import "Chapter.h"#import "TextContent.h"@interface AppDelegate : UIResponder <UIApplicationDelegate>@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];        // 設定資料庫路徑    NSURL *url = [[[NSFileManager defaultManager]                   URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask]lastObject];    NSURL *storeDataBaseURL = [url URLByAppendingPathComponent:@"BOOKS.sqlite"];        // 建立presistentStoreCoordinator    NSError *error = nil;    NSPersistentStoreCoordinator *presistentStoreCoordinator  = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[NSManagedObjectModel mergedModelFromBundles: nil]];        // 指定儲存類型和路徑    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

// 儲存新對象-(void) testStore{    // 從AppDelegate 獲得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];    // 第一個章節    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;        // 第二個章節    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;        // 書籍對象    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];        // 提交到持久儲存    if ([context hasChanges]) {        [context save:nil];    }}// 讀取對象-(void) testRead{    // 從AppDelegate 獲得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 產生查詢對象 （查詢全部資料）    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 執行查詢    NSError *error;    NSArray *arrayBooks = [context executeFetchRequest:request error:&error];    // 定義排序方式 （根據集合中Chapter對象的orderId屬性排序，升序）    NSSortDescriptor *chaptersDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"orderId" ascending:YES];        // 遍曆結果集    for (Book *book in arrayBooks) {                // 使用當前對象屬性        NSLog(@"book name = %@", book.name);                // 使用當前對象的集合屬性，轉成數組        NSArray *arrayChapters = [book.myChapters allObjects];                // 排序        arrayChapters = [arrayChapters                          sortedArrayUsingDescriptors:[NSArray arrayWithObjects:chaptersDescriptor,nil]];                // 遍曆子數組        for (Chapter *chapter in arrayChapters) {            NSLog(@"chapter name = %@", chapter.name);                        TextContent *content = (TextContent*) chapter.myContent;            NSLog(@"chapter text = %@", content.text);        }    }}// 更新對象屬性-(void) testUpdate{    // 從AppDelegate 獲得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 產生Request對象    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 執行查詢    NSError *error;    NSArray *array = [context executeFetchRequest:request error:&error];        // 更改對象屬性    Book * book = array[0];    book.name = @"BOOKS";        // 提交到持久儲存    if ([context hasChanges]) {        [context save:nil];    }}// 刪除對象-(void) testRemove{    // 從AppDelegate 獲得context    AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;    NSManagedObjectContext *context = [appDelegate managedObjectContext];        // 產生Request對象    NSEntityDescription *entityDescr = [NSEntityDescription entityForName:@"Book" inManagedObjectContext:context];    NSFetchRequest *request = [[NSFetchRequest alloc]init];    [request setEntity:entityDescr];        // 執行查詢    NSError *error;    NSArray *array = [context executeFetchRequest:request error:&error];        // 遍曆刪除對象,因為在模型裡把關係設定為Cascade,所以子物件會被自動刪除    for (Book *book in array) {        [context deleteObject:book];    }        // 提交到持久儲存    if ([context hasChanges]) {        [context save:nil];    }}

 

iOS: Core Data入門