MagicalRecord配合Mantle
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;
快速入门后续的例子都是以此实体进行数据库的操作
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];
插入数据
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。
[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) {
// ...
}];
为什么不用[NSManagedObjectContext save:]方法，请看博客
配合Mantle
基本转换
上一篇博文中提到Mantle的<MTLManagedObjectSerializing>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，因为Member类的字段名是相同，所以这里返回nil
+ (NSDictionary *)managedObjectKeysByPropertyKey{
return nil;
}
//表示Member的url向MemberManaged的url字段值转换
+ (NSValueTransformer *)entityAttributeTransformerForKey:(NSString *)key{
if ([key isEqualToString:@"url"]) {
return [MTLValueTransformer reversibleTransformerWithBlock:^id(NSURL *url) {
return url.absoluteString;
}];
}
else{
return nil;
}
}
具体运用：
NSDictionary *dic = @{@"id" : @"1",
@"phone" : @"xxxxxxxx",
@"date" : @"2014-09-09",
@"goldNumber" : @2,
@"age" : @"28",
@"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(@"%@", [(MemberManaged *)[MemberManaged MR_findFirst] isVip]);
}];
- 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"];
}
执行一下代码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。
for (int n = 0; n < 2; n++) {
NSDictionary *dic = @{@"id" : @"1",
@"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(@"%d", [(MemberManaged *)[MemberManaged MR_findFirst] isVip].boolValue);
}];
}
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