Question

我有两个数组，一个是来自核心数据（array1）的获取请求的数组，另一个是来自Web（array2）的数据。我想要做的是将array1与array2进行比较，并且array2中不在array1中的任何项都需要添加到core-data中。

我从中提取的数据与每个人都有关联。当我创建一个新的“人”实体时，我也用它保存了这个id。我不确定如何使用Person的id比较数组，甚至不知道如何在数组中访问它。

以下是获取请求：

NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
    NSError *error = nil;
    [fetch setEntity:[NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.managedObjectContext]];
    NSSortDescriptor *sorter = [NSSortDescriptor sortDescriptorWithKey:@"Pid" ascending:YES];
    request.sortDescriptors = @[sorter];
    NSArray *items = [self.managedObjectContext executeFetchRequest:request error:&error];

我按照相同的方式对fetch进行排序，并对新数据进行排序。我只是不确定如何比较两者，然后将新项目添加到核心数据中。请帮帮忙？

更新

    NSDictionary *qDict = [JSON objectForKey:@"person"];
        NSArray *qArry = [JSON objectForKey:@"person"];

//Used to print the id's
        _testArray = [NSMutableArray arrayWithArray:[qDict valueForKey:@"id"]];
        for (NSNumber *numb in _testArray) {
            NSLog(@"id = %@", numb);
        }


        NSError *error = nil;
        NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Pid IN %@", [qDict valueForKey:@"Pid"]];
        [fetchRequest setPredicate:predicate];
        [fetchRequest setSortDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"Pid" ascending:YES]]];
        NSArray *items = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
        NSLog(@"%d how many items from the fetch", items.count);

        for (NSDictionary *qdt in qArry) {

            NSUInteger currentIndex = 0;
            Person *q = nil;

            if ([items count] > currentIndex) {
                q = [items objectAtIndex:currentIndex];
            }

            if ([q.Pid integerValue] == [[qdt objectForKey:@"id"] integerValue]) {
                // Either update the object or just move on

            }

            else {
                // Add the object to core data
                q = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.managedObjectContext];
                q.url = [qdt valueForKey:@"url"];
                q.Pid = [qdt objectForKey:@"id"];
                q.text = [qdt valueForKey:@"personText"];
                NSError *error = nil;
                [_managedObjectContext save:&error];


            }
            currentIndex++;
        }

        //[_managedObjectContext save:&error];

    }
            failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON)  {
                UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error retrieving data" message:@"Please try again" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];

                [av show];


            }];

Answer 1

也许你可以这样做：

NSMutableArray *webData = [NSMutableArray arrayWithObjects:@"object 1",@"object 2",@"object 3",@"object 4", nil];
NSMutableArray *coreData = [NSMutableArray arrayWithObjects:@"object 2",@"object 4", nil];

NSMutableArray *newData = [NSMutableArray arrayWithArray:webData];
[newData removeObjectsInArray:coreData];

//output "object 1", "object 3"

或者如果您在数组中有自定义NSObject并将其与主键进行比较，那么您可以执行以下操作：

NSMutableArray *webData = [NSMutableArray arrayWithObjects:test1,test2,test3,test4, nil];
NSMutableArray *coreData = [NSMutableArray arrayWithObjects:test2,test3, nil];



__block NSMutableArray *newData = [NSMutableArray new];
[webData enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    __block testObject *object = (testObject *)obj;

    __block BOOL isExisting = NO;
    [coreData enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        testObject *innerObject = (testObject *)obj;
        if(object._id == innerObject._id)
            isExisting = YES;
    }];
    if(!isExisting)
        [newData addObject:object];
}];
//output will be object 1 and object 4

Answer 2

首先，您可以根据您从网络上检索的人员ID（idArray）获取核心数据中存储的对象列表，并根据ID对其进行排序：

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id IN %@", idArray];
[fetchRequest setPredicate:predicate];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"id" ascending:YES]]];

这将返回在您从Web检索的对象中也可以找到id的对象列表。我们称之为storedRecords数组。然后，您可以执行以下操作：

设置一个计数器，
遍历downloadedArray（这是包含从网络检索到的对象的数组，也必须按id 排序），
在storedRecords数组中使用objectAtIndex，
检查storedManagedObject的id是否与记录对象的id匹配如果它不匹配，则它是一个可以保存到核心数据中的新对象。否则，它是一个现有对象。
增加柜台。

以下是一个例子：

int currentIndex = 0;
for (NSDictionary *record in downloadedArray) {
    NSManagedObject *storedManagedObject = nil;
    if ([storedRecords count] > currentIndex) {
        storedManagedObject = [storedRecords objectAtIndex:currentIndex];
    }
    if ([[storedManagedObject valueForKey:@"id"] integerValue] == [[record valueForKey:@"id"] integerValue]) {
        //this will be existing object in core data
        //you can update the object if you want
    } else {
        //this will be new object that you can store into core data
    }
    currentIndex++;
}

这与此处提到的类似：

http://www.raywenderlich.com/15916/how-to-synchronize-core-data-with-a-web-service-part-1

Answer 3

试试这个

NSMutableArray *array1 = [[NSMutableArray alloc] initWithObjects:@"a",@"a",@"a",@"d",@"b",@"b",@"c",@"a",@"c",nil];

NSMutableArray *array2 = [[NSMutableArray alloc] initWithObjects:[NSString stringWithFormat:@"%@",[array1 objectAtIndex:0]], nil];;

for(int i = 0;i<[array1 count];i++)
{
    if ([array2 containsObject:[array1 objectAtIndex:i]]) {
        NSLog(@"do nothing");
    }
    else{
        [array2 addObject:[array1 objectAtIndex:i]];
        NSLog(@"array2 is %@",array2);
    }
    NSLog(@"finally array2 is %@",array2);

}

array2将为{ a,d,b,c }

比较两个数组的内容并找出差异

3 个答案: