CoreData Entity ImportFromApi, before import(Find-or-Create), we delete local not exist data first.

ImportFromApi

//
//  NSManagedObject+ImportFromApi.m
//  ThermometerBLE
//
//  Created by Tonny on 3/4/14.
//  Copyright (c) 2014 Doouya. All rights reserved.
//

#import "NSManagedObject+ImportFromApi.h"
#import "CommunityHeader.h"

@implementation NSManagedObject (ImportFromApi)

+ (void) DY_importFromArray:(NSArray *)array completion:(DYIndexBlock)completion
{
    [self DY_importFromArray:array importBlock:nil deletePredicateBlock:nil completion:completion];
}

+ (void) DY_importFromArray:(NSArray *)array importBlock:(DYTwoObjectBlock)importBlock deletePredicateBlock:(DYPredicateBlock)predicateBlock completion:(DYIndexBlock)completion{
#ifdef DEBUG
    __block NSPredicate *deletePre = nil;
    NSDate *startD = [NSDate date];
    NSMutableArray *needUpdateIds = [NSMutableArray arrayWithCapacity:array.count];
    NSMutableArray *add = [NSMutableArray arrayWithCapacity:array.count];
#endif
    
    NSUInteger count = array.count;
    [NSManagedObjectContext childSaveWithBlock:^(NSManagedObjectContext *localContext) {//use default context instead of child of root context
        NSAttributeDescription *primaryAttribute = [[self MR_entityDescription] MR_primaryAttributeToRelateBy]; //topicId
        NSString *key = [primaryAttribute name]; //topicId
        
        if (predicateBlock) { //delete
            NSPredicate *pre = nil;
            if (count > 0) {
                id first = [[array firstObject] MR_valueForAttribute:primaryAttribute];
                id last = [[array lastObject] MR_valueForAttribute:primaryAttribute];
                NSInteger max = MAX([first integerValue], [last integerValue]);
                NSInteger min = MIN([first integerValue], [last integerValue]);
                
                NSArray *values = [array valueForKeyPath:[[primaryAttribute userInfo] valueForKey:kMagicalRecordImportAttributeKeyMapKey]]; //id
                pre = predicateBlock(key, min, max, values, localContext);
            }else{ //0
                pre = predicateBlock(key, 0, 0, nil, localContext);
            }
            
            if (pre) {
#ifdef DEBUG
                SLLog(@"delete pre %@", pre);
                deletePre = pre;
                
                NSArray *deleted = [self MR_findAllWithPredicate:pre inContext:localContext];
                SLog(@"Import Delete %@ %@", NSStringFromClass([self class]), [[deleted valueForKeyPath:key] componentsJoinedByString:@","]);
#endif
                [self MR_deleteAllMatchingPredicate:pre inContext:localContext];
            }
        }
        
        if (count > 0) {
            ///update
            NSArray *allIds = [array valueForKeyPath:@"id"];
            NSPredicate *updatePre = [NSPredicate predicateWithFormat:@"%K IN %@", key, allIds];
            NSArray *exist = [self MR_findAllWithPredicate:updatePre inContext:localContext];
            NSMutableArray *needUpdate = exist.count>0?[exist mutableCopy]:nil;
            
            [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                id Id = obj[@"id"];
                NSManagedObject *mamObj = nil;
                if (needUpdate && needUpdate.count > 0) { //update
                    NSInteger location = [[needUpdate valueForKeyPath:key] indexOfObject:Id];
                    if (location != NSNotFound) {
                        mamObj = needUpdate[location];
                        [needUpdate removeObject:mamObj];
#ifdef DEBUG
                        [needUpdateIds addObject:Id];
#endif
                    }
                }
                
                if (!mamObj) {
#ifdef DEBUG
                    [add addObject:Id];
#endif
                    
                    mamObj = [self MR_createInContext:localContext]; //create
                }
                
                [mamObj MR_importValuesForKeysWithObject:obj];
                
                if (importBlock) {
                    importBlock(obj, mamObj);
                }
            }];
            
            //delete repeat data
            SLog(@"Import Delete Repeate %@ %@", NSStringFromClass([self class]), [[needUpdate valueForKeyPath:key] componentsJoinedByString:@","]);
            
            [needUpdate enumerateObjectsUsingBlock:^(NSManagedObject *obj, NSUInteger idx, BOOL *stop) {
                [obj MR_deleteInContext:localContext];
            }];
            
            SLog(@"Import Update %@ %@", NSStringFromClass([self class]), [needUpdateIds componentsJoinedByString:@","]);
            SLog(@"Import Add %@ %@", NSStringFromClass([self class]), [add componentsJoinedByString:@","]);
        }
    } completion:^(BOOL success, NSError *error) {
            completion(count);
#ifdef DEBUG
            if (deletePre) {
                NSAssert([self MR_countOfEntitiesWithPredicate:deletePre] == 0, @"Something wrong?");
            }
             
            NSTimeInterval intervalD = [startD timeIntervalSinceNow];
            SLLog(@"timeInterval %f", ABS(intervalD));
#endif
    }];
}

@end

1. Delete local data
2. Find-Or-Create, to update local exist data and create new data
3. Delete repeat data

Improve:

1. import in batches to low memory used.