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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;
@endFunction＋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");
}
}];
}时间： 2024-07-30 18:42:48