Core Data with Mantle

Mantle makes it easy to write a simple model layer for your Cocoa or Cocoa Touch application. Mantle can still be a convenient translation layer between the API and your managed model objects.

本文使用mantle作data model，並使用其對coredata的interface創建數據持久化的過程。

操作過程很簡單，就是數據的轉換：

1.Manle data model

Mantle中用於持久化的方法：

// A MTLModel object that supports being serialized to and from Core Data as an

// NSManagedObject.

• @protocol MTLManagedObjectSerializing
• @required

  // The name of the Core Data entity that the receiver serializes to and

  // deserializes from.

  • + (NSString *)managedObjectEntityName;

    // Specifies how to map property keys to different keys on the receiver's

    // +managedObjectEntity.

    • + (NSDictionary *)managedObjectKeysByPropertyKey;
      

      .h 文件

      [objc] view plaincopyprint?
      1. #import
      3. @interface BannerWrapper : MTLModel
      5. @property (nonatomic, readonly) bool result;
      6. @property (copy, nonatomic, readonly) NSNumber *resultId;
      7. @property (copy, nonatomic, readonly) NSString *resultMsg;
      8. @property (copy, nonatomic) NSArray *bannerList;
      9. +(NSSortDescriptor *)sortDescriptor;
      10. @end
      12. @interface Banner : MTLModel
      14. @property (copy, nonatomic, readonly) NSNumber *bannerId;
      15. @property (copy, nonatomic, readonly) NSString *picUrl;
      16. @property (copy, nonatomic, readonly) NSString *toDetailUrl;
      17. @property (copy, nonatomic, readonly) NSNumber *width;
      18. @property (copy, nonatomic, readonly) NSNumber *height;
      20. @end
          
          

          .m文件

          [objc] view plaincopyprint?
          1. #import "Banner.h"
          3. @implementation BannerWrapper
          5. #pragma mark - JSON serialization
          7. + (NSDictionary *)JSONKeyPathsByPropertyKey {
          8. return @{
          9. @"result" : @"result",
          10. @"resultId" : @"resultId",
          11. @"resultMsg" : @"resultMSG",
          12. @"bannerList" : @"banner"
          13. };
          14. }
          16. + (NSValueTransformer *)bannerListJSONTransformer
          17. {
          18. return [NSValueTransformer mtl_JSONArrayTransformerWithModelClass:[Banner class]];
          19. }
          21. #pragma mark - Managed object serialization
          23. + (NSString *)managedObjectEntityName {
          24. return @"BannerWrapper";
          25. }
          27. + (NSDictionary *)managedObjectKeysByPropertyKey {
          28. return nil;
          29. }
          31. +(NSDictionary *)relationshipModelClassesByPropertyKey{
          32. return @{
          33. @"bannerList" : [Banner class],
          34. };
          35. }
          37. //在從coredata中取數據時的數據排序方式
          38. +(NSSortDescriptor *)sortDescriptor{
          39. return [[NSSortDescriptor alloc] initWithKey:@"resultId" ascending:YES];
          40. }
          42. @end
          44. @implementation Banner
          46. #pragma mark - JSON serialization
          48. + (NSDictionary *)JSONKeyPathsByPropertyKey {
          49. return @{
          50. @"bannerId" : @"id",
          51. @"picUrl" : @"picUrl",
          52. @"toDetailUrl" : @"toDetailUrl",
          53. @"width":@"width",
          54. @"height":@"height"
          55. };
          56. }
          58. #pragma mark - Managed object serialization
          60. + (NSString *)managedObjectEntityName {
          61. return @"Banner";
          62. }
          64. + (NSDictionary *)managedObjectKeysByPropertyKey {
          65. return nil;
          66. }
          68. @end
              
              

              2.coredata 持久化類

              Coredata主要元素簡要介紹

              網上有很多圖，但，還是覺得一本書上的這個圖最好：

              
              

              • 1， Managed Object Model
                Managed Object Model 是描述應用程序的數據模型，這個模型包含實體（Entity），特性（Property），讀取請求（Fetch Request）等。（下文都使用英文術語。）
                
                2，Managed Object Context
                Managed Object Context 參與對數據對象進行各種操作的全過程，並監測數據對象的變化，以提供對 undo/redo 的支持及更新綁定到數據的 UI。
                
                3，Persistent Store Coordinator
                Persistent Store Coordinator 相當於數據文件管理器，處理底層的對數據文件的讀取與寫入。一般我們無需與它打交道。
                
                4，Managed Object
                Managed Object 數據對象，與 Managed Object Context 相關聯。
              • 
                5，Controller
                圖中綠色的 Array Controller, Object Controller, Tree Controller 這些控制器，一般都是通過 control+drag 將 Managed Object Context 綁定到它們，這樣我們就可以在 nib 中可視化地操作數據。
                

                .h文件

                [objc] view plaincopyprint?
                1. #import
                3. @interface Persistence : NSObject
                5. //數據模型對象
                6. @property(strong,nonatomic) NSManagedObjectModel *managedObjectModel;
                7. //上下文對象
                8. @property(strong,nonatomic) NSManagedObjectContext *managedObjectContext;
                9. //持久性存儲區
                10. @property(strong,nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
                12. //確定sqlite文件存儲路徑
                13. -(NSURL *)storeURL;
                15. //初始化Core Data使用的數據庫
                16. -(NSPersistentStoreCoordinator *)persistentStoreCoordinator;
                18. //managedObjectModel的初始化賦值函數
                19. -(NSManagedObjectModel *)managedObjectModel;
                21. //managedObjectContext的初始化賦值函數
                22. -(NSManagedObjectContext *)managedObjectContext;
                24. //保存MTLModel對象至coredata
                25. -(BOOL)saveMTLModel:(MTLModel *)mtlModel
                26. error:(NSError * __autoreleasing *)error;
                28. //從coredata中提取出MTLModel
                29. -(MTLModel *)getMTLmodel:(MTLModel *)mtlModel
                30. error:(NSError *__autoreleasing *)error;
                32. //+ (NSFetchRequest *)fetchRequest;
                33. @end
                    
                    

                    
                    

                    
                    

                    .m文件

                    [objc] view plaincopyprint?
                    1. #import "Persistence.h"
                    3. @implementation Persistence
                    5. @synthesize managedObjectContext;
                    6. @synthesize managedObjectModel;
                    7. @synthesize persistentStoreCoordinator;
                    10. //確定sqlite文件存儲路徑
                    11. -(NSURL *)storeURL{
                    12. //得到數據庫的路徑
                    13. // NSString *docs = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
                    14. // //CoreData是建立在SQLite之上的，數據庫名稱需與Xcdatamodel文件同名
                    15. // NSURL *storeUrl = [NSURL fileURLWithPath:[docs stringByAppendingPathComponent:@"CoreData.sqlite"]];
                    17. NSArray *documnetDir=NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES);
                    18. NSString *docDir=[documnetDir objectAtIndex:0];
                    19. NSString *path=[docDir stringByAppendingPathComponent:@"CoreData.sqlite"];
                    20. NSURL *storeURL=[NSURL fileURLWithPath:path];
                    21. return storeURL;
                    22. }
                    25. //初始化Core Data使用的數據庫
                    26. -(NSManagedObjectModel *)managedObjectModel
                    27. {
                    28. if (managedObjectModel != nil) {
                    29. return managedObjectModel;
                    30. }
                    31. return [NSManagedObjectModel mergedModelFromBundles:nil];
                    32. }
                    34. //managedObjectModel的初始化賦值函數
                    35. -(NSPersistentStoreCoordinator *)persistentStoreCoordinator
                    36. {
                    37. if (persistentStoreCoordinator != nil) {
                    38. return persistentStoreCoordinator;
                    39. }
                    41. NSError *error = nil;
                    42. persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]
                    43. initWithManagedObjectModel:self.managedObjectModel];
                    44. if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
                    45. configuration:nil
                    46. URL:[self storeURL]
                    47. options:nil
                    48. error:&error]) {
                    49. NSLog(@"Error: %@,%@",error,[error userInfo]);
                    50. [NSException raise:@"open failed" format:@"Reason:%@",[error localizedDescription]];
                    51. }
                    53. return persistentStoreCoordinator;
                    54. }
                    56. //managedObjectContext的初始化賦值函數
                    57. -(NSManagedObjectContext *)managedObjectContext
                    58. {
                    59. if (managedObjectContext != nil) {
                    60. return managedObjectContext;
                    61. }
                    63. NSPersistentStoreCoordinator *coordinator =self.persistentStoreCoordinator;
                    65. if (coordinator != nil) {
                    66. managedObjectContext = [[NSManagedObjectContext alloc]init];
                    67. [managedObjectContext setPersistentStoreCoordinator:coordinator];
                    68. }
                    70. return managedObjectContext;
                    71. }
                    73. //保存MTLModel對象至coredata
                    74. -(BOOL)saveMTLModel:(MTLModel *)mtlModel
                    75. error:(NSError *__autoreleasing *)error{
                    76. //-----Need Add Remove the Entity First START---------
                    77. NSManagedObject *exsitManagedObject=[self getManagedObject:mtlModel
                    78. error:error];
                    79. if (exsitManagedObject!=nil) {
                    80. [self.managedObjectContext deleteObject:exsitManagedObject];
                    81. [self.managedObjectContext save:error];
                    82. };
                    83. //-----Need Add Remove the Entity First END-----------
                    85. NSManagedObject *managedObject = [MTLManagedObjectAdapter
                    86. managedObjectFromModel:mtlModel
                    87. insertingIntoContext:self.managedObjectContext
                    88. error:error];
                    90. if (managedObject==nil) {
                    91. NSLog(@"[NSManagedObject] Error:%@",*error);
                    92. return NO;
                    93. }
                    95. if (![self.managedObjectContext save:error]) {
                    96. NSLog(@"[self.managedObjectContext] Error:%@",*error);
                    97. return NO;
                    98. };
                    99. return YES;
                    100. };
                    102. //從coredata中提取出MTLModel
                    103. -(MTLModel *)getMTLmodel:(MTLModel *)mtlModel
                    104. error:(NSError *__autoreleasing *)error{
                    106. NSManagedObject *managedObject=[self getManagedObject:mtlModel error:error];
                    107. MTLModel *mrlMotel=[[MTLModel alloc] init];
                    109. mrlMotel = [MTLManagedObjectAdapter modelOfClass:[mtlModel class]
                    110. fromManagedObject:managedObject error:error];
                    112. if (error) {
                    113. NSLog(@"[mrlMotel] Error:%@",*error);
                    114. }
                    115. return mrlMotel;
                    116. };
                    118. //從coredata中獲取已存的ManagedObject
                    119. -(NSManagedObject *)getManagedObject:(MTLModel *)mtlModel
                    120. error:(NSError *__autoreleasing *)error{
                    121. NSString *entityName=[[mtlModel class] managedObjectEntityName];
                    123. //獲取entity中對象數量
                    124. NSFetchRequest *requestCount=[NSFetchRequest fetchRequestWithEntityName:entityName];
                    125. NSUInteger count=[self.managedObjectContext countForFetchRequest:requestCount
                    126. error:error];
                    127. NSLog(@"count result:%d",count);
                    128. NSLog(@"sortDescriptor result:%@",[[mtlModel class] sortDescriptor]);
                    130. //獲取entity中第一個對象.這個對象必須存在且唯一。
                    131. if (count==1) {
                    132. NSFetchRequest *request=[[NSFetchRequest alloc] init];
                    133. [request setEntity:[NSEntityDescription entityForName:entityName
                    134. inManagedObjectContext:self.managedObjectContext]];
                    135. NSSortDescriptor *sort=[[mtlModel class] sortDescriptor];
                    136. NSArray *sortDes=[[NSArray alloc] initWithObjects:sort, nil nil];
                    137. [request setSortDescriptors:sortDes];
                    138. NSArray *getObject=[self.managedObjectContext
                    139. executeFetchRequest:request
                    140. error:error];
                    142. return [getObject objectAtIndex:0];
                    143. }
                    144. return nil;
                    145. }
                    147. //從文件系統中刪除sqlite文件
                    148. -(bool)deleteAllEntities{
                    149. bool status=NO;
                    150. NSError *error;
                    151. @try{
                    152. [[NSFileManager defaultManager] removeItemAtPath:[self storeURL].path
                    153. error:&error];
                    154. status=YES;
                    155. }
                    156. @catch (NSException *exception) {
                    157. status=NO;
                    158. }
                    159. @finally {
                    160. return status;
                    161. }
                    162. }
                    164. @end
                         
                         
                         3.後台執行程序
                         [objc] view plaincopyprint?
                         1. - (void)loadBannerList:(void (^)(NSArray *bannerList, NSError *error))block {
                         3. NSParameterAssert(block);
                         5. [self POST:@"webresources/homePage"
                         6. parameters:nil
                         7. resultClass:BannerWrapper.class
                         8. resultKeyPath:nil
                         9. completion:^(AFHTTPRequestOperation *operation, id responseObject, NSError *error) {
                         11. //-----------------------Persistence DEMO---------------------
                         12. //If network error, get data from CoreData, else save data into CoreData
                         13. if (!error) {
                         14. NSError *err;
                         15. Persistence *persistence=[[Persistence alloc] init];
                         16. BOOL save=[persistence saveMTLModel:responseObject error:&err];
                         17. if (save==NO) {
                         18. NSLog(@"Save ERROR!");
                         19. }
                         20. }else{
                         21. NSError *err;
                         22. Persistence *persistence=[[Persistence alloc] init];
                         23. BannerWrapper *resObject=[[BannerWrapper alloc] init];
                         24. BannerWrapper *object=[[BannerWrapper alloc] init];
                         25. object=[persistence getMTLmodel:resObject error:&err];
                         27. responseObject=object;
                         29. //這個地方異常的奇怪，從coredata中應該返回打Array類型變成了set類型，所以這裡暫時作了一個轉換。
                         30. if ([object.bannerList isKindOfClass:[NSSet class]]) {
                         31. NSArray *objectArray = [(NSSet *)object.bannerList allObjects];
                         32. ((BannerWrapper *)responseObject).bannerList=objectArray;
                         33. }
                         34. }
                         35. //-----------------------------------------------------------
                         37. BannerWrapper *wrapper = responseObject;
                         38. block(wrapper.bannerList, error);
                         40. }];
                         41. }