除了使用SQL關(guān)系數(shù)據(jù)庫外，我們還可以使用Xcode中提供的核心數(shù)據(jù)來處理表結(jié)構(gòu)數(shù)據(jù)，今天就讓武林技術(shù)頻道帶大家一起進入下文了解詳解iOS應用開發(fā)中Core Data數(shù)據(jù)存儲的使用吧，希望對你學習有幫助！
1.如果想創(chuàng)建一個帶有coreData的程序,要在項目初始化的時候勾選中
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2.創(chuàng)建完成之后,會發(fā)現(xiàn)在AppDelegate里多出了幾個屬性,和2個方法
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@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;?
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;?
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;?
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- (void)saveContext;?
- (NSURL *)applicationDocumentsDirectory;?
Core Data數(shù)據(jù)持久化是對SQLite的一個升級，它是ios集成的，在說Core Data之前，我們先說說在CoreData中使用的幾個類。
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（1）NSManagedObjectModel(被管理的對象模型)
相當于實體，不過它包含 了實體間的關(guān)系
(2)NSManagedObjectContext(被管理的對象上下文)
操作實際內(nèi)容
作用：插入數(shù)據(jù)? 查詢? 更新? 刪除
（3）NSPersistentStoreCoordinator(持久化存儲助理)
相當于數(shù)據(jù)庫的連接器
(4)NSFetchRequest(獲取數(shù)據(jù)的請求)
相當于查詢語句
(5)NSPredicate(相當于查詢條件)
(6)NSEntityDescription(實體結(jié)構(gòu))
(7)后綴名為.xcdatamodel的包
里面的.xcdatamodel文件，用數(shù)據(jù)模型編輯器編輯
編譯后為.momd或.mom文件，這就是為什么文件中沒有這個東西，而我們的程序中用到這個東西而不會報錯的原因。
3.如果想創(chuàng)建一個實體對象的話,需要點擊.xcdatamodel,Add Entity,添加想要的字段
4.生成對象文件,command+n,然后選中CoreData里的NSManagerObjectSubClass進行關(guān)聯(lián),選中實體創(chuàng)建
5.添加數(shù)據(jù)
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Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.managedObjectContext];?
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??? if (newPerson == nil){?
??????? NSLog(@"Failed to create the new person.");?
??????? return NO;?
??? }?
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??? newPerson.firstName = paramFirstName;?
??? newPerson.lastName = paramLastName;?
??? newPerson.age = [NSNumber numberWithUnsignedInteger:paramAge];?
??? NSError *savingError = nil;?
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??? if ([self.managedObjectContext save:&savingError]){?
??????? return YES;?
??? } else {?
??????? NSLog(@"Failed to save the new person. Error = %@", savingError);?
??? }?
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NSEntityDescription（實體結(jié)構(gòu)）相當于表格結(jié)構(gòu)
6.取出數(shù)據(jù)查詢
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/* Create the fetch request first */?
??? NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];?
??? /* Here is the entity whose contents we want to read */?
??? NSEntityDescription *entity =?
??? [NSEntityDescription?
???? entityForName:@"Person"?
???? inManagedObjectContext:self.managedObjectContext];?
??? /* Tell the request that we want to read the
???? contents of the Person entity */?
??? [fetchRequest setEntity:entity];?
??? NSError *requestError = nil;?
??? /* And execute the fetch request on the context */?
??? NSArray *persons =?
??? [self.managedObjectContext executeFetchRequest:fetchRequest?
???????????????????????????????????????????? error:&requestError];?
??? /* Make sure we get the array */?
??? if ([persons count] > 0){?
??????? /* Go through the persons array one by one */?
??????? NSUInteger counter = 1;?
??????? for (Person *thisPerson in persons){?
??????????? NSLog(@"Person %lu First Name = %@",?
????????????????? (unsigned long)counter,??
????????????????? thisPerson.firstName);??
??????????? NSLog(@"Person %lu Last Name = %@",??
????????????????? (unsigned long)counter,??
????????????????? thisPerson.lastName);?
??????????? NSLog(@"Person %lu Age = %ld",?
????????????????? (unsigned long)counter,?
????????????????? (unsigned long)[thisPerson.age unsignedIntegerValue]);?
??????????? counter++;?
??????? }?
??? } else {?
??????? NSLog(@"Could not find any Person entities in the context.");??
??? }?
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7.刪除數(shù)據(jù)
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/* Create the fetch request first */?
??? NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];?
??? /* Here is the entity whose contents we want to read */?
??? NSEntityDescription *entity =?
??? [NSEntityDescription?
???? entityForName:@"Person"?
???? inManagedObjectContext:self.managedObjectContext];?
??? /* Tell the request that we want to read the
???? contents of the Person entity */?
??? [fetchRequest setEntity:entity];?
??? NSError *requestError = nil;?
??? /* And execute the fetch request on the context */?
??? NSArray *persons =?
??? [self.managedObjectContext executeFetchRequest:fetchRequest?
???????????????????????????????????????????? error:&requestError];?
??? if ([persons count] > 0){?
??????? /* Delete the last person in the array */?
??????? Person *lastPerson = [persons lastObject];?
??????? [self.managedObjectContext deleteObject:lastPerson];?
??????? NSError *savingError = nil;?
??????? if ([self.managedObjectContext save:&savingError]){?
??????????? NSLog(@"Successfully deleted the last person in the array.");?
??????? } else {?
??????????? NSLog(@"Failed to delete the last person in the array.");?
??????? }?
??? } else {??
??????? NSLog(@"Could not find any Person entities in the context.");??
??? }??
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8.排序
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NSSortDescriptor *ageSort =?? [[NSSortDescriptor alloc] initWithKey:@"age"?? ascending:YES];?? NSSortDescriptor *firstNameSort =?? [[NSSortDescriptor alloc] initWithKey:@"firstName"?? ascending:YES];?? NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:?? ageSort,?? firstNameSort, nil nil];?? fetchRequest.sortDescriptors = sortDescriptors;
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注意ascending:YES 屬性決定排序順序?
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