iOS 数据持久化之CoreData（二）堆栈建立和基本操作Demo

原创Blog，转载请注明出处
blog.csdn.net/hello_hwc
欢迎关注我的iOS SDK详解专栏
http://blog.csdn.net/column/details/huangwenchen-ios-sdk.html

---

前言：本文会通过一个完整的工程创建，讲解

• CoreData的堆栈创建
• 四种基本的操作（查询，创建，删除，更新）
• 简单的MVC设计
• 如何使用Block传递Action，缩减代码量
• 再CoreData使用类别扩展NSManagedObject方法

---

Demo下载
http://download.csdn.net/detail/hello_hwc/8692083

注意，这个Demo侧重讲解如何建立CoreData堆栈，以及常见的四种操作，为后续文章的讲解做铺垫的，所以非常简单，简单到体现不到CoreData的优点，如果你哪怕写过一个使用了CoreData的工程，那就这篇就可以直接不看了。

---

Demo效果

四种基本操作

点击Query All
Log输出

2015-05-13 10:26:13.534 QuiteSimpeCoreDataDemo[3029:62136] (    "name:Lucy age:21",    "name:Tom age:20",    "name:jack age:21")

然后，添加一个新的Person，点击Create

输出

2015-05-13 10:27:03.764 QuiteSimpeCoreDataDemo[3029:62136] Create Successfully.Id is 0xd000000000100000 <x-coredata://ACB1C333-E7B3-4D6A-BF58-7061952D95AD/Person/p4>

然后更新

---

输出

2015-05-13 10:28:21.109 QuiteSimpeCoreDataDemo[3029:62136] Update Successfully

在查询全部，看到年龄更新成功

2015-05-13 10:30:06.557 QuiteSimpeCoreDataDemo[3029:62136] (    "name:Lily age:24",    "name:Lucy age:21",    "name:Tom age:20",    "name:jack age:21")

删除

输出

2015-05-13 10:31:27.312 QuiteSimpeCoreDataDemo[3029:62136] Delete successfully

再查询，发现删除成功

2015-05-13 10:31:42.711 QuiteSimpeCoreDataDemo[3029:62136] (    "name:Lucy age:21",    "name:Tom age:20",    "name:jack age:21")

---

Demo的建立过程

• 新建一个工程,注意选中使用CoreData

• 查看AppDelegate.m，会发现很多和CoreData创建堆栈相关的代码，为了代码的解耦合，把这些代码以AppDelegate.m中的代码拷贝到一个新建类（Store）中，这个类点作用就是创建堆栈，提供NSManagedContext
  Store.h

#import <Foundation/Foundation.h>#import <CoreData/CoreData.h>@interface Store : NSObject@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;- (void)saveContext;- (NSURL *)applicationDocumentsDirectory;@end

再看看Store.m各个部分的内容

//获取DocumentDirectory- (NSURL *)applicationDocumentsDirectory {    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];}

获取对象图模型，这里的对象图名字就是这个文件的名字

- (NSManagedObjectModel *)managedObjectModel {    if (_managedObjectModel != nil) {        return _managedObjectModel;    }    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"QuiteSimpeCoreDataDemo" withExtension:@"momd"];    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];    return _managedObjectModel;}

创建持久化存储协调器

 - (NSPersistentStoreCoordinator *)persistentStoreCoordinator {    if (_persistentStoreCoordinator != nil) {        return _persistentStoreCoordinator;    }        _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"QuiteSimpeCoreDataDemo.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]) {        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];        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);        abort();//这里为了方便调试，正常的App不要这样写    }    return _persistentStoreCoordinator;}

创建Managed Context

- (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;}

保存到磁盘

 - (void)saveContext {    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;    if (managedObjectContext != nil) {        NSError *error = nil;        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);            abort();        }    }}

---

• 点击QuiteSimpleCoreDataDemo.xcdatamodeld,创建一个Entity，命名为Person，添加两个属性，name和age，如图
  

---

• Editor－ CreateNSManaged Subclass － 一致勾选－创建声称两个文件，Person.h,Person.m

  

---

创建Person的类别Function＋Person，在这里为NSManagedObject添加方法，不要在类中直接添加，因为下次在自动生成时候会把这之前的覆盖掉。
Function＋Person.h文件

#import "Person.h"@interface Person (Functions)+(NSString *)entityName;+(Person *)insertNewObjectInManagedObjectContext:(NSManagedObjectContext *) context;@end

Function＋Person.m文件

#import "Person+Functions.h"@implementation Person (Functions)+(NSString *)entityName{    return @"Person";}+(Person *)insertNewObjectInManagedObjectContext:(NSManagedObjectContext *) context{    return [NSEntityDescription insertNewObjectForEntityForName:[self entityName] inManagedObjectContext:context];}//重写Description，方便Log-(NSString *)description{    return [NSString stringWithFormat:@"name:%@ age:%ld",self.name,(long)self.age.integerValue];}@end

---

然后，回到viewController进行相关的处理
使用AlertController作为输入，创建一个公共方法，这里的CoreDataAction是我定义的一个Block，传入如何处理数据的动作。

typedef void(^CoreDataAction)(NSString * name,NSString * age);

-(void)AlertTextFieldWithTitle:(NSString *)actionTitle Action:(CoreDataAction) actionBlock {    UIAlertController * alert = [UIAlertController alertControllerWithTitle:actionTitle message:nil preferredStyle:UIAlertControllerStyleAlert];    [alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {       textField.placeholder = @"Name";    }];    [alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {        textField.placeholder = @"age";    }];    [alert addAction:[UIAlertAction actionWithTitle:actionTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {        NSArray * textfields = alert.textFields;        UITextField * nameTextfields = textfields[0];        UITextField * ageTextFields = textfields[1];        actionBlock(nameTextfields.text,ageTextFields.text);    }]];    [alert addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil]];    [self presentViewController:alert animated:YES completion:nil];}

---

查询当前Name的Person是否存在（本工程Person的name不允许重复），存在则返回，不存在则返回nil

-(Person *)personExistWithName:(NSString *)name{    NSFetchRequest * fetchRequest = [NSFetchRequest fetchRequestWithEntityName:[Person entityName]];    //This is an array    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"name =  %@",name];    NSError *error = nil;    NSArray *fetchedObjects = [self.store.managedObjectContext executeFetchRequest:fetchRequest error:&error];    if (fetchedObjects == nil) {        return nil;    }else{        return [fetchedObjects lastObject];    }}

---

对应的四个Button的target－action
查询

- (IBAction)queryAll:(id)sender {    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];    NSEntityDescription *entity = [NSEntityDescription entityForName:[Person entityName] inManagedObjectContext:self.store.managedObjectContext];    [fetchRequest setEntity:entity];    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name"                                                                   ascending:YES];    [fetchRequest setSortDescriptors:[NSArray arrayWithObjects:sortDescriptor, nil]];    NSError *error = nil;    NSArray *fetchedObjects = [self.store.managedObjectContext executeFetchRequest:fetchRequest error:&error];    if (fetchedObjects == nil) {        NSLog(@"It is empty");    }else{        NSLog(@"%@",fetchedObjects.description);    }}

---

更新

- (IBAction)update:(id)sender {    [self AlertTextFieldWithTitle:@"Update" Action:^(NSString *name, NSString *age) {        Person * person = [self personExistWithName:name];        if (person != nil) {            person.age = @(age.integerValue);            [self.store saveContext];            NSLog(@"Update Successfully");        }else{            NSLog(@"Person does not exist,can not update");        }    }];}

---

创建

- (IBAction)Create:(id)sender {    [self AlertTextFieldWithTitle:@"Create" Action:^(NSString *name, NSString *age) {        if ([self personExistWithName:name] == nil) {            Person * person = [Person insertNewObjectInManagedObjectContext:self.store.managedObjectContext];            person.name = name;            person.age =  @(age.integerValue);            [self.store saveContext];            NSLog(@"Create Successfully.Id is %@",person.objectID.description);        }else{            NSLog(@"This peson  exist before,can not create");        }    }];}

---

删除

- (IBAction)Delete:(id)sender {    [self AlertTextFieldWithTitle:@"Delete" Action:^(NSString *name, NSString *age) {        Person * person = [self personExistWithName:name];        if (person != nil) {            [self.store.managedObjectContext deleteObject:person];            NSLog(@"Delete successfully");        }else{            NSLog(@"This does not exist before,can not delete");        }    }];}

---