使用CoreData [1]

標籤：des   style   blog   http   color   使用   os   io   

使用CoreData [1]

本篇教程能教你從無開始接觸CoreData,包括建立工程,建立出實體,增刪改查樣樣都有,屬於使用CoreData最初級教程.

 

1. 建立帶有CoreData的工程項目

 

2. 添加一個實體類

 

3. 建立出實體類

 

4. 建立對象,儲存對象,執行代碼

以下是驗證結果:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    NSLog(@"%@", NSHomeDirectory());        // 實體描述資訊    NSEntityDescription *description =         [NSEntityDescription entityForName:@"Student"                    inManagedObjectContext:[self managedObjectContext]];        // 初始化對象    Student *student = [[Student alloc] initWithEntity:description                        insertIntoManagedObjectContext:[self managedObjectContext]];    student.name     = @"YouXianMing";    student.age      = [NSNumber numberWithInt:26];        // 儲存對象    [self saveContext];    return YES;}

這樣就實現了儲存物件.

 

5. 重複上面的步驟儲存5個對象.

 

6. 遍曆出所有的對象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    // 設定要查詢的實體    NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Student"];        // 取出查詢結果    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];        // 遍曆    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        Student *student = obj;        NSLog(@"%@ %@", student.age, student.name);    }];    return YES;}

 

7. 刪除一個對象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    // 設定要查詢的實體    NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Student"];        // 取出查詢結果    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];        // 遍曆    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        Student *student = obj;        // 找到匹配的資料,刪除之        if ([student.name isEqualToString:@"QiuLiang"])        {            [[self managedObjectContext] deleteObject:student];        }    }];        // 儲存    [self saveContext];        // 遍曆    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        Student *student = obj;                NSLog(@"%@ %@", student.age, student.name);    }];    return YES;}

 

8. 修改一個對象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    // 設定要查詢的實體    NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Student"];        // 取出查詢結果    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];        // 遍曆    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        Student *student = obj;        // 找到匹配的資料,修改之        if ([student.name isEqualToString:@"YouXianMing"])        {            student.age = [NSNumber numberWithInt:100];        }    }];        // 儲存    [self saveContext];        // 遍曆    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        Student *student = obj;                NSLog(@"%@ %@", student.age, student.name);    }];    return YES;}

 

9. 根據謂詞尋找出實體的方法請自行百度腦補,這裡不贅述了.