iOS简单数据库操作集成：MagicalRecord + YYM

使用MagicalRecord对CoreData的二次封装进行数据库操作

使用cocoapods引入MagicalRecord和YYModel库。
源码和用法看github就可以了：
MagicalRecord: MagicalRecord git
YYModel: YYModel git

Demo: MagicalRecord+YYModel

---

使用YYModel自动转换json数据为CoreData模型对象，YYModel不支持CoreData模型的转换，这里利用runtime写了一个分类"NSManagedObject+Common"，用以支持CoreData的转换。

思路是：

1. 在Entity Class中实现分类中要调用的方法"primaryKeys"用来指定自定义主键，"coreDataModelContainerPropertyGenericClass"指定容器属性（relation）中的元素类，modelPropertyBlacklist屏蔽relation的普通赋值。
2. 读取json数据，解析成字典。
3. 使用MagicalRecord创建DB Entity，再使用YYModel赋值。
4. 使用runtime，探测出此Entity中的relation，并递归调用上一步的创建Entity和赋值逻辑。
5. 存入数据库。

NSManagedObject+Common.h

@interface NSManagedObject (Common)

+ (NSArray *)getAllObjects:(NSManagedObjectContext *)context;
+ (void)deleteAllObjects:(NSManagedObjectContext *)context;

+ (instancetype)getObjectWithPrimaryKeyPredicates:(NSArray *)predicates context:(NSManagedObjectContext *)context;
+ (void)deleteObjectWithPrimaryKeyPredicates:(NSArray *)predicates context:(NSManagedObject *)context;

+ (instancetype)insertOrReplaceWithDictionary:(NSDictionary *)dict context:(NSManagedObjectContext *)context;
+ (NSArray *)insertWithArray:(NSArray *)array context:(NSManagedObjectContext *)context;

// 原NSManagedObject需要实现的方法
+ (NSArray *)primaryKeys;
+ (NSDictionary *)coreDataModelContainerPropertyGenericClass;

@end

NSManagedObject+Common.m

#import "NSManagedObject+Common.h"
#import <objc/message.h>
#import <objc/runtime.h>

#define ENTITY_NAME NSStringFromClass([self class])

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wincomplete-implementation"
@implementation NSManagedObject (Common)
#pragma clang diagnostric pop

+ (NSArray *)getAllObjects:(NSManagedObjectContext *)context {
    return [self MR_findAllWithPredicate:nil inContext:context];
}

+ (void)deleteAllObjects:(NSManagedObjectContext *)context {
    if (!context) {
        return;
    }
    
    NSArray *objects = [self getAllObjects:context];
    for (NSManagedObject *object in objects) {
        [object MR_deleteEntityInContext:context];
        [context MR_saveToPersistentStoreAndWait];
    }
}

+ (instancetype)getObjectWithPrimaryKeyPredicates:(NSArray *)predicates context:(NSManagedObjectContext *)context {
    if (!predicates || !context) {
        return nil;
    }
    
    NSMutableString *preStr = [NSMutableString string];
    NSArray *primaryKeys = [self primaryKeys];
    if (predicates.count != primaryKeys.count) {
        return nil;
    }
    
    for (int i=0; i<primaryKeys.count; i++) {
        NSString *predicateKey = primaryKeys[i];
        NSObject *value = predicates[i];
        
        if ([value isKindOfClass:[NSString class]]) {
            [preStr appendString:[NSString stringWithFormat:@" (%@ = \"%@\") ", predicateKey, value]];
            
        } else {
            [preStr appendString:[NSString stringWithFormat:@" (%@ = %@) ", predicateKey, value]];
        }
        
        if (i != primaryKeys.count - 1) {
            [preStr appendString:@" AND "];
        }
    }
    
    return [self MR_findFirstWithPredicate:[NSPredicate predicateWithFormat:preStr] inContext:context];
}

+ (void)deleteObjectWithPrimaryKeyPredicates:(NSArray *)predicates context:(NSManagedObjectContext *)context {
    NSManagedObject *object = [self getObjectWithPrimaryKeyPredicates:predicates context:context];
    [object MR_deleteEntityInContext:context];
    [context MR_saveToPersistentStoreAndWait];
}

+ (instancetype)insertOrReplaceWithDictionary:(NSDictionary *)dict context:(NSManagedObjectContext *)context {
    if (!dict || !context) {
        return nil;
    }
    
    NSMutableArray *predicates = [NSMutableArray array];
    for (NSString *primaryKey in [self primaryKeys]) {
        [predicates addObject:[dict valueForKey:primaryKey]];
    }
    
    NSManagedObject *object = [self getObjectWithPrimaryKeyPredicates:predicates context:context];
    if (!object) {
        object = [self MR_createEntityInContext:context];
    }
    
    [context MR_saveToPersistentStoreAndWait];
    
    [object yy_modelSetWithDictionary:dict];
    [object handleRelationsWithDictionary:dict context:context];
    
    [context MR_saveToPersistentStoreAndWait];
    
    return object;
}

+ (NSArray *)insertWithArray:(NSArray *)array context:(NSManagedObjectContext *)context {
    if (!array || !context) {
        return nil;
    }
    
    NSMutableArray *result = [NSMutableArray arrayWithCapacity:array.count];
    for (NSDictionary *dict in array) {
        NSManagedObject *object = [self insertOrReplaceWithDictionary:dict context:context];
        [result addObject:object];
    }
    
    return result;
}

// 处理容器类属性，传入的dictionary中的NSArray，NSDictionary
- (void)handleRelationsWithDictionary:(NSDictionary *)dict context:(NSManagedObjectContext *)context {
    [dict enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSObject *obj, BOOL * _Nonnull stop) {
        if ([obj isKindOfClass:[NSArray class]]) {
            objc_property_t property = class_getProperty([self class], key.UTF8String);
            
            if ([[self class] respondsToSelector:@selector(coreDataModelContainerPropertyGenericClass)]) {
                NSDictionary *classDict = [[self class] coreDataModelContainerPropertyGenericClass];
                
                NSString *key = [NSString stringWithUTF8String:property_getName(property)];
                Class c = [classDict objectForKey:key];
                NSArray *savedRelationObjects = [c insertWithArray:(NSArray *)obj context:context];
                
                [self setValue:[NSSet setWithArray:savedRelationObjects] forKey:key];
                [context MR_saveToPersistentStoreAndWait];
            }
            
        } else if ([obj isKindOfClass:[NSDictionary class]]) {
            objc_property_t property = class_getProperty([self class], key.UTF8String);
            NSString *key = [NSString stringWithUTF8String:property_getName(property)];
            
            unsigned int count = 0;
            objc_property_attribute_t *attrs = property_copyAttributeList(property, &count);
            for (int i=0; i<count; i++) {
                objc_property_attribute_t attr = attrs[i];
                
                NSString *attrName = [NSString stringWithUTF8String:attr.name];
                if ([@"T" isEqualToString:attrName]) { // 属性类名key是"T"
                    NSString *className = [NSString stringWithUTF8String:attr.value]; // 这是带有"@"和双引号的类名字符串，例如@"User"
                    className = [className stringByReplacingOccurrencesOfString:@"@" withString:@""];
                    className = [className stringByReplacingOccurrencesOfString:@"\"" withString:@""];
                    Class c = NSClassFromString(className);
                    
                    NSManagedObject *savedRelationObject = [c insertOrReplaceWithDictionary:(NSDictionary *)obj context:context];
                    
                    [self setValue:savedRelationObject forKey:key];
                    [context MR_saveToPersistentStoreAndWait];
                    
                    break;
                }
            }
        }
        
    }];
}

@end

这里列举一个实体模型HVWBoy要实现的方法：

#import "HVWBoy.h"
#import "HVWGirl.h"

@implementation HVWBoy

// Insert code here to add functionality to your managed object subclass
// 自定义的“主键”，为了插入的时候不造成数据“冗余”，因为每次插入数据是CoreData自己生成真正的主键的
+ (NSArray *)primaryKeys {
    return @[@"pid"];
}

// 容器元素类，使用了NSManagedObject+Common，需要实现这个类似于YYModel中containerPropertyGenericClass的方法，用来指明容器属性中元素的类型
+ (NSDictionary *)coreDataModelContainerPropertyGenericClass {
    return @{@"girlfriends" : [HVWGirl class]};
}

// 黑名单，因为YYModel并不能自动进行转换，需要先屏蔽容器类属性
+ (NSArray *)modelPropertyBlacklist {
    return @[@"girlfriends"];
}

@end

调用：
ViewController

#import "ViewController.h"
#import "HVWBoy.h"
#import "HVWGirl.h"
#import "NSManagedObject+Common.h"

@interface ViewController ()

- (IBAction)readJsonAndSave:(UIButton *)sender;
- (IBAction)readAllBoysFromDB:(UIButton *)sender;
- (IBAction)cleanDBData:(UIButton *)sender;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


- (IBAction)readJsonAndSave:(UIButton *)sender {
    NSString *json = @"{\"data\":[{\"girlfriends\":[{\"pid\":200,\"name\":\"Judy\"},{\"pid\":201,\"name\":\"Summer\"},{\"pid\":202,\"name\":\"Sufia\"}],\"pid\":100,\"name\":\"John\",\"nick\":\"Programer\",\"age\":25},{\"girlfriends\":[{\"pid\":203,\"name\":\"Aoi\"}],\"pid\":101,\"name\":\"Peter\",\"nick\":\"PM\",\"age\":30}]}";
    
    NSData *jsonData = [json dataUsingEncoding:NSUTF8StringEncoding];
    NSDictionary *dataDic = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:NULL];
    
    // 在使用NSManagedObject+Common之前，需要手动先创建实例，再进行字典转模型，且不能处理容器属性
    //    NSManagedObjectContext *context = [NSManagedObjectContext MR_rootSavingContext];
    //
    //    for (NSDictionary *dic in [dataDic objectForKey:@"data"]) {
    //        HVWBoy *boy = [HVWBoy MR_findFirstWithPredicate:[NSPredicate predicateWithFormat:@"pid = %d", [[dic objectForKey:@"pid"] intValue]]];
    //        if (!boy) {
    //            boy = [HVWBoy MR_createEntityInContext:context];
    //        }
    //
    //        [boy yy_modelSetWithDictionary:dic];
    //        [context MR_saveToPersistentStoreAndWait];
    //    }
    
    // 使用NSManagedObject+Common之后
    NSManagedObjectContext *context = [NSManagedObjectContext MR_rootSavingContext];
    
    // 只需要调用一个方法，就可以自动从json转换到Core模型对象并存储
    [HVWBoy insertWithArray:[dataDic objectForKey:@"data"] context:context];
    
    NSLog(@"Save data into DB succeeded!");
}

- (IBAction)readAllBoysFromDB:(UIButton *)sender {
    //    NSManagedObjectContext *context = [NSManagedObjectContext MR_defaultContext];
    NSArray *boys = [HVWBoy MR_findAll];
    
    if (!boys.count) {
        NSLog(@"No data in DB!");
        return;
    }
    
    for (HVWBoy *boy in boys) {
        NSLog(@"boy --> pid:%lld, name:%@, age:%d, nick:%@", boy.pid, boy.name, boy.age, boy.nick);
        
        for (HVWGirl *girl in boy.girlfriends) {
            NSLog(@"%@'s girlfriend --> pid:%lld, name:%@", boy.name, girl.pid, girl.name);
        }
    }
}

- (IBAction)cleanDBData:(UIButton *)sender {
    NSArray *boys = [HVWBoy MR_findAll];
    for (HVWBoy *boy in boys) {
        [boy MR_deleteEntity];
        [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait];
    }
    
    NSLog(@"Clean DB succeeded");
}

@end