MagicalRecord

King

•

在开始之前，我们先创建一个名为MemberManaged的实体

MemberManaged.h

@interface MemberManaged : NSManagedObject
@property (nonatomic, retain) NSString * memberID;
@property (nonatomic, retain) NSString * mobilePhone;
@property (nonatomic, retain) NSDate * createDate;
@property (nonatomic, retain) NSNumber * goldNumber;
@property (nonatomic, retain) NSNumber * age;
@property (nonatomic, retain) NSNumber * isVip;
@property (nonatomic, retain) NSString * url;

后续的例子都是以此实体进行数据库的操作

快速入门

配置

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [MagicalRecord setupAutoMigratingCoreDataStack];
    // ...
    return YES;
}
- (void)applicationWillTerminate:(UIApplication *)application
{
    [MagicalRecord cleanUp];
}

查找数据

//返回MemberManaged表中的第一条数据
MemberManaged *memberManaged = [MemberManaged MR_findFirst];

//返回MemberManaged表中的所有数据NSArray *array = [[MemberManaged MR_findAll];

//键值条件查找，返回符合条件的所有数据NSArray *array = [MemberManaged MR_findByAttribute:@"memberID" withValue:@"1"];

//按指定字段排序NSArray *array = [MemberManaged MR_findAllSortedBy:@"age" ascending:YES];

//自定义NSPredicate查找，返回符合条件的所有数据NSPredicate *pre = [NSPredicate predicateWithFormat:@"age > 18"];MemberManaged *memberManaged = [MemberManaged MR_findAllWithPredicate:pre];

对于NSPredicate不熟悉的同学可以看我之前写的介绍NSPredicate的博文，关于其他的查找方法我就不一一介绍了。

插入数据

    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        MemberManaged *memberManaged = [MemberManaged MR_createInContext:localContext];        memberManaged.memberID = @"1";        memberManaged.mobilePhone = @"xxxxxxxx";        memberManaged.createDate = [NSDate date];        memberManaged.goldNumber = @2;        memberManaged.age = @18;        memberManaged.url = @"http://bawn.github.io/";        memberManaged.isVip = @YES;    } completion:^(BOOL success, NSError *error) {        // ...    }];

删除数据

//删除单条数据   [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        MemberManaged *member = [MemberManaged MR_findFirstInContext:localContext];        [member MR_deleteEntity];    } completion:^(BOOL success, NSError *error) {        // ...    }];

//删除表    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        [MemberManaged MR_truncateAllInContext:localContext];    } completion:^(BOOL success, NSError *error) {        // ...    }];

更新数据

    MemberManaged *member = [MemberManaged MR_findFirst];    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        MemberManaged *localMember = [member MR_inContext:localContext];        localMember.age = @22;    } completion:^(BOOL success, NSError *error) {        // ...    }];

配合Mantle

基本转换

上一篇博文中提到Mantle的 MTLManagedObjectAdapter 类，2.0版本开发者已把此类作为一个单独 repo 从 Mantle 剥离出来，这个类有个名叫MTLManagedObjectSerializing的协议，此协议有两个必须实现的方法:

//返回此类对应的实体类名+ (NSString *)managedObjectEntityName;

//返回此类和实体属性的映射关系+ (NSDictionary *)managedObjectKeysByPropertyKey;

另外由于Member类和MemberManaged类的url字段的类型不一致，需要实现另一个协议方法，实现NSUrl–>NSString（age和isVip字段不需要转换，不要问我为什么）

//属性值转换+ (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key;

先看具体实现

Member.h

@interface Member : MTLModel<MTLJSONSerializing, MTLManagedObjectSerializing>@property (nonatomic, retain) NSString   * memberID;@property (nonatomic, retain) NSString   * mobilePhone;@property (nonatomic, retain) NSDate     * createDate;@property (nonatomic, retain) NSNumber   *goldNumber;@property (nonatomic, assign) NSUInteger age;@property (nonatomic, assign) BOOL       isVip;@property (nonatomic, retain) NSURL      *url;

Member.m

//表示Member类对应的实体类是MemberManaged+ (NSString *)managedObjectEntityName{    return @"MemberManaged";}

//表示Member类向MemberManaged类转换的字段映射，也是需要写全的+ (NSDictionary *)managedObjectKeysByPropertyKey{    return @{             @"memberID" : @"memberID",             @"mobilePhone" : @"mobilePhone",             @"createDate" : @"createDate",             @"goldNumber" : @"goldNumber",             @"age" : @"age",             @"isVip" : @"isVip",             @"url" : @"url"             };}

具体运用：

    NSDictionary *dic = @{  @"id" : @"2",                          @"phone" : @"xxxxxxxx",                          @"date" : @"2014-09-09",                          @"goldNumber" : @2,                          @"age" : @"18",                          @"url" : @"http://bawn.github.io/",                          @"isVip" : NSNull.null                          };    Member *member = [MTLJSONAdapter modelOfClass:[Member class] fromJSONDictionary:dic error:nil];    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        [MTLManagedObjectAdapter managedObjectFromModel:member insertingIntoContext:localContext error:nil];    } completion:^(BOOL success, NSError *error) {        NSLog(@"%lu", (unsigned long)[MemberManaged MR_findAll].count);    }];

Member *member = [MTLJSONAdapter modelOfClass:[Member class] fromJSONDictionary:dic error:nil]; 完成从NSDictionary–>Member转换，并返回Member实例
[MTLManagedObjectAdapter managedObjectFromModel:member insertingIntoContext:localContext error:nil]; 完成Member–>MemberManaged转换，返回MemberManaged实例，但是我们并不需要。
配合MagicalRecord储存方法+ (void) saveWithBlock:(void(^)(NSManagedObjectContext *localContext))block;

注意：对于MemberManaged类，我们并不需要对它做任何的处理。

唯一性检查

同样是实现<MTLManagedObjectSerializing>中的一个方法：

+ (NSSet *)propertyKeysForManagedObjectUniquing{    return [NSSet setWithObject:@"memberID"];}

表示当插入新数据的时候，对比需要插入的这条数据的memberID字段的值是否和数据库中的有相同。如果有相同就覆盖更新这条数据，如果没有就新增。这样带来的方便之处显而易见。

更新数据

- (IBAction)updateData:(id)sender{    NSDictionary *dic = @{  @"id" : @"2",                          @"phone" : @"xxxxxxxx",                          @"date" : @"2015-12-09",                          @"goldNumber" : @2,                          @"age" : @"19",                          @"url" : @"http://bawn.github.io/",                          @"isVip" : NSNull.null                          };    Member *member = [MTLJSONAdapter modelOfClass:[Member class] fromJSONDictionary:dic error:nil];    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {        [MTLManagedObjectAdapter managedObjectFromModel:member insertingIntoContext:localContext error:nil];    } completion:^(BOOL success, NSError *error) {        NSLog(@"%lu", (unsigned long)[MemberManaged MR_findAll].count);    }];}

数据库中只有一条数据，因为插入的数据的memberID都是2。

总结

MagicalRecord配合Mantle使用至少让代码看起来简洁了不少，再也不用为Core Data复杂的API而烦恼，也不用再写if/else来做字段的转换。

Demo地址：MagicalRecord-Mantle

原文:大专栏 MagicalRecord

计算机

2022年2月04日