如何使用UISearchDisplayController / UISearchBar过滤NSFetchedResultsController（CoreData）

我正在尝试在基于CoreData的iPhone应用程序中实现搜索代码。我不确定如何进行。该应用程序已经具有一个NSFetchedResultsController，该谓词可以检索主TableView的数据。我想确保在更改过多代码之前，我走在正确的道路上。我很困惑，因为这么多示例都是基于数组而不是CoreData的。

这里有一些问题：

1. 我是否需要第二个NSFetchedResultsController仅检索匹配项，还是可以使用与主要TableView相同的项？

2. 如果使用相同的方法，是否简单到清除FRC缓存，然后更改handleSearchForTerm：searchString方法中的谓词？谓词是否必须包含初始谓词以及搜索词，或者它还记得它最初使用谓词来检索数据吗？

3. 我如何回到原始结果？我是否只是将搜索谓词设置为nil？这样一来就不会杀死用于检索FRC结果的原始谓词吗？

如果有人在使用FRC进行搜索时有任何代码示例，我将不胜感激！

我实际上只是在我的一个项目中实现了这一点（您的问题和另一个错误的答案暗示了要做什么）。我尝试了Sergio的答案，但是在设备上实际运行时出现异常问题。

是的，您创建了两个获取结果控制器：一个用于常规显示，另一个用于UISearchBar的表视图。

如果仅使用一个FRC（NSFetchedResultsController），则原始UITableView（而不是搜索时处于活动状态的搜索表视图）可能会在搜索时调用回调，并尝试错误地使用过滤后的FRC版本，并且会看到异常抛出错误的节数或节中的行数。

这是我做的事情：我有两个FRC可用，分别作为属性fetchedResultsController和searchFetchedResultsController。除非进行搜索，否则不应该使用searchFetchedResultsController（取消搜索后，您可以在下面看到该对象已释放）。所有UITableView方法都必须弄清楚它将查询哪个表视图以及从中提取信息的适用FRC。FRC委托方法还必须找出要更新的tableView。

令人惊讶的是，其中有多少是样板代码。

头文件的相关位：

@interface BlahViewController : UITableViewController <UISearchBarDelegate, NSFetchedResultsControllerDelegate, UISearchDisplayDelegate> 
{
    // other class ivars

    // required ivars for this example
    NSFetchedResultsController *fetchedResultsController_;
    NSFetchedResultsController *searchFetchedResultsController_;
    NSManagedObjectContext *managedObjectContext_;

    // The saved state of the search UI if a memory warning removed the view.
    NSString        *savedSearchTerm_;
    NSInteger       savedScopeButtonIndex_;
    BOOL            searchWasActive_;
}
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSFetchedResultsController *fetchedResultsController;

@property (nonatomic, copy) NSString *savedSearchTerm;
@property (nonatomic) NSInteger savedScopeButtonIndex;
@property (nonatomic) BOOL searchWasActive;

实现文件的相关位：

@interface BlahViewController ()
@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
@property (nonatomic, retain) NSFetchedResultsController *searchFetchedResultsController;
@property (nonatomic, retain) UISearchDisplayController *mySearchDisplayController;
@end

当使用所有UITableViewDelegate / DataSource方法时，我创建了一个有用的方法来检索正确的FRC：

- (NSFetchedResultsController *)fetchedResultsControllerForTableView:(UITableView *)tableView
{
    return tableView == self.tableView ? self.fetchedResultsController : self.searchFetchedResultsController;
}

- (void)fetchedResultsController:(NSFetchedResultsController *)fetchedResultsController configureCell:(UITableViewCell *)theCell atIndexPath:(NSIndexPath *)theIndexPath
{
    // your cell guts here
}

- (UITableViewCell *)tableView:(UITableView *)theTableView cellForRowAtIndexPath:(NSIndexPath *)theIndexPath
{
    CallTableCell *cell = (CallTableCell *)[theTableView dequeueReusableCellWithIdentifier:@"CallTableCell"];
    if (cell == nil) 
    {
        cell = [[[CallTableCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"CallTableCell"] autorelease];
    }

    [self fetchedResultsController:[self fetchedResultsControllerForTableView:theTableView] configureCell:cell atIndexPath:theIndexPath];
    return cell;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 
{
    NSInteger count = [[[self fetchedResultsControllerForTableView:tableView] sections] count];

    return count;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{
    NSInteger numberOfRows = 0;
    NSFetchedResultsController *fetchController = [self fetchedResultsControllerForTableView:tableView];
    NSArray *sections = fetchController.sections;
    if(sections.count > 0) 
    {
        id <NSFetchedResultsSectionInfo> sectionInfo = [sections objectAtIndex:section];
        numberOfRows = [sectionInfo numberOfObjects];
    }

    return numberOfRows;

}

代表搜索栏的方法：

#pragma mark -
#pragma mark Content Filtering
- (void)filterContentForSearchText:(NSString*)searchText scope:(NSInteger)scope
{
    // update the filter, in this case just blow away the FRC and let lazy evaluation create another with the relevant search info
    self.searchFetchedResultsController.delegate = nil;
    self.searchFetchedResultsController = nil;
    // if you care about the scope save off the index to be used by the serchFetchedResultsController
    //self.savedScopeButtonIndex = scope;
}


#pragma mark -
#pragma mark Search Bar 
- (void)searchDisplayController:(UISearchDisplayController *)controller willUnloadSearchResultsTableView:(UITableView *)tableView;
{
    // search is done so get rid of the search FRC and reclaim memory
    self.searchFetchedResultsController.delegate = nil;
    self.searchFetchedResultsController = nil;
}

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    [self filterContentForSearchText:searchString 
                               scope:[self.searchDisplayController.searchBar selectedScopeButtonIndex]];

    // Return YES to cause the search result table view to be reloaded.
    return YES;
}


- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption
{
    [self filterContentForSearchText:[self.searchDisplayController.searchBar text] 
                               scope:[self.searchDisplayController.searchBar selectedScopeButtonIndex]];

    // Return YES to cause the search result table view to be reloaded.
    return YES;
}

从FRC委托方法获取更新时，请确保使用正确的表视图：

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller 
{
    UITableView *tableView = controller == self.fetchedResultsController ? self.tableView : self.searchDisplayController.searchResultsTableView;
    [tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller 
  didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex 
     forChangeType:(NSFetchedResultsChangeType)type 
{
    UITableView *tableView = controller == self.fetchedResultsController ? self.tableView : self.searchDisplayController.searchResultsTableView;

    switch(type) 
    {
        case NSFetchedResultsChangeInsert:
            [tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controller:(NSFetchedResultsController *)controller 
   didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)theIndexPath 
     forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath 
{
    UITableView *tableView = controller == self.fetchedResultsController ? self.tableView : self.searchDisplayController.searchResultsTableView;

    switch(type) 
    {
        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:theIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self fetchedResultsController:controller configureCell:[tableView cellForRowAtIndexPath:theIndexPath] atIndexPath:theIndexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:theIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller 
{
    UITableView *tableView = controller == self.fetchedResultsController ? self.tableView : self.searchDisplayController.searchResultsTableView;
    [tableView endUpdates];
}

其他查看信息：

- (void)loadView 
{   
    [super loadView];
    UISearchBar *searchBar = [[[UISearchBar alloc] initWithFrame:CGRectMake(0, 0, self.tableView.frame.size.width, 44.0)] autorelease];
    searchBar.autoresizingMask = (UIViewAutoresizingFlexibleWidth);
    searchBar.autocorrectionType = UITextAutocorrectionTypeNo;
    self.tableView.tableHeaderView = searchBar;

    self.mySearchDisplayController = [[[UISearchDisplayController alloc] initWithSearchBar:searchBar contentsController:self] autorelease];
    self.mySearchDisplayController.delegate = self;
    self.mySearchDisplayController.searchResultsDataSource = self;
    self.mySearchDisplayController.searchResultsDelegate = self;
}

- (void)didReceiveMemoryWarning
{
    self.searchWasActive = [self.searchDisplayController isActive];
    self.savedSearchTerm = [self.searchDisplayController.searchBar text];
    self.savedScopeButtonIndex = [self.searchDisplayController.searchBar selectedScopeButtonIndex];

    fetchedResultsController_.delegate = nil;
    [fetchedResultsController_ release];
    fetchedResultsController_ = nil;
    searchFetchedResultsController_.delegate = nil;
    [searchFetchedResultsController_ release];
    searchFetchedResultsController_ = nil;

    [super didReceiveMemoryWarning];
}

- (void)viewDidDisappear:(BOOL)animated
{
    // save the state of the search UI so that it can be restored if the view is re-created
    self.searchWasActive = [self.searchDisplayController isActive];
    self.savedSearchTerm = [self.searchDisplayController.searchBar text];
    self.savedScopeButtonIndex = [self.searchDisplayController.searchBar selectedScopeButtonIndex];
}

- (void)viewDidLoad
{
    // restore search settings if they were saved in didReceiveMemoryWarning.
    if (self.savedSearchTerm)
    {
        [self.searchDisplayController setActive:self.searchWasActive];
        [self.searchDisplayController.searchBar setSelectedScopeButtonIndex:self.savedScopeButtonIndex];
        [self.searchDisplayController.searchBar setText:savedSearchTerm];

        self.savedSearchTerm = nil;
    }
}

FRC创建代码：

- (NSFetchedResultsController *)newFetchedResultsControllerWithSearch:(NSString *)searchString
{
    NSArray *sortDescriptors = // your sort descriptors here
    NSPredicate *filterPredicate = // your predicate here

    /*
     Set up the fetched results controller.
     */
    // Create the fetch request for the entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *callEntity = [MTCall entityInManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:callEntity];

    NSMutableArray *predicateArray = [NSMutableArray array];
    if(searchString.length)
    {
        // your search predicate(s) are added to this array
        [predicateArray addObject:[NSPredicate predicateWithFormat:@"name CONTAINS[cd] %@", searchString]];
        // finally add the filter predicate for this view
        if(filterPredicate)
        {
            filterPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:filterPredicate, [NSCompoundPredicate orPredicateWithSubpredicates:predicateArray], nil]];
        }
        else
        {
            filterPredicate = [NSCompoundPredicate orPredicateWithSubpredicates:predicateArray];
        }
    }
    [fetchRequest setPredicate:filterPredicate];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                                                                                managedObjectContext:self.managedObjectContext 
                                                                                                  sectionNameKeyPath:nil 
                                                                                                           cacheName:nil];
    aFetchedResultsController.delegate = self;

    [fetchRequest release];

    NSError *error = nil;
    if (![aFetchedResultsController performFetch:&error]) 
    {
        /*
         Replace this implementation with code to handle the error appropriately.

         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return aFetchedResultsController;
}    

- (NSFetchedResultsController *)fetchedResultsController 
{
    if (fetchedResultsController_ != nil) 
    {
        return fetchedResultsController_;
    }
    fetchedResultsController_ = [self newFetchedResultsControllerWithSearch:nil];
    return [[fetchedResultsController_ retain] autorelease];
}   

- (NSFetchedResultsController *)searchFetchedResultsController 
{
    if (searchFetchedResultsController_ != nil) 
    {
        return searchFetchedResultsController_;
    }
    searchFetchedResultsController_ = [self newFetchedResultsControllerWithSearch:self.searchDisplayController.searchBar.text];
    return [[searchFetchedResultsController_ retain] autorelease];
}   

有人评论说这可以用一个来完成NSFetchedResultsController。这就是我所做的，这是详细信息。该解决方案假定您只想过滤表并维护搜索结果的所有其他方面（排序顺序，单元格布局等）。

首先，在您的 UITableViewController子类中（使用相应的@synthesize和dealloc（如果适用））：

@property (nonatomic, retain) UISearchDisplayController *searchController;
@property (nonatomic, retain) NSString *searchString;

其次，在 viewDidLoad:UITableViewController子类方法中：

UISearchBar *searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(0,0,self.tableView.frame.size.width,44)]; 
searchBar.placeholder = @"Search";
searchBar.delegate = self;
self.searchController = [[[UISearchDisplayController alloc] initWithSearchBar:searchBar contentsController:self] autorelease];
self.searchController.delegate = self;
self.searchController.searchResultsDataSource = self;   
self.searchController.searchResultsDelegate = self; 
self.tableView.tableHeaderView = self.searchController.searchBar;
[searchBar release];

第三，实施 UISearchDisplayController委托方法：

// This gets called when you start typing text into the search bar
-(BOOL)searchDisplayController:(UISearchDisplayController *)_controller shouldReloadTableForSearchString:(NSString *)_searchString {
   self.searchString = _searchString;
   self.fetchedResultsController = nil;
   return YES;
}

// This gets called when you cancel or close the search bar
-(void)searchDisplayController:(UISearchDisplayController *)controller willUnloadSearchResultsTableView:(UITableView *)tableView {
   self.searchString = nil;
   self.fetchedResultsController = nil;
   [self.tableView reloadData];
}

最后，在fetchedResultsController方法中更改NSPredicate依赖关系是否 self.searchString已定义：

-(NSFetchedResultsController *)fetchedResultsController {
   if (fetchedResultsController == nil) {

       // removed for brevity

      NSPredicate *predicate;

      if (self.searchString) {
         // predicate that uses searchString (used by UISearchDisplayController)
         // e.g., [NSPredicate predicateWithFormat:@"name CONTAINS[cd] %@", self.searchString];
          predicate = ... 
      } else {
         predicate = ... // predicate without searchString (used by UITableViewController)
      }

      // removed for brevity

   }

   return fetchedResultsController;
} 

我花了一些力气才能使它工作...

我理解的关键是意识到这里有两个tableViews在起作用。一个由我的viewcontroller管理，一个由searchviewcontroller管理，然后我可以进行测试以查看哪个处于活动状态并做正确的事情。该文档也很有帮助：

http://developer.apple.com/library/ios/#documentation/uikit/reference/UISearchDisplayController_Class/Reference/Reference.html

这是我所做的-

添加了searchIsActive标志：

@interface ItemTableViewController : UITableViewController <NSFetchedResultsControllerDelegate, UISearchDisplayDelegate, UISearchBarDelegate> {

    NSString *sectionNameKeyPath;
    NSArray *sortDescriptors;


@private
    NSFetchedResultsController *fetchedResultsController_;
    NSManagedObjectContext *managedObjectContext_;

    BOOL searchIsActive;

}

@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
@property (nonatomic, retain) NSString *sectionNameKeyPath;
@property (nonatomic, retain) NSArray *sortDescriptors;
@property (nonatomic) BOOL searchIsActive;

在实现文件中添加了综合功能。

然后，我将这些方法添加到搜索中：

#pragma mark -
#pragma mark Content Filtering

- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
    NSFetchRequest *aRequest = [[self fetchedResultsController] fetchRequest];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH[cd] %@", searchText];

    [aRequest setPredicate:predicate];

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
        // Handle error
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }  

}

#pragma mark -
#pragma mark UISearchDisplayController Delegate Methods

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    [self filterContentForSearchText:[self.searchDisplayController.searchBar text] scope:nil];

    return YES;
}

/*
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchScope:(NSInteger)searchOption
{
    return YES;
}
*/

- (void)searchDisplayControllerWillBeginSearch:(UISearchDisplayController *)controller {
    [self setSearchIsActive:YES];
    return;
}

- (void)searchDisplayControllerDidEndSearch:(UISearchDisplayController *)controller 
{
    NSFetchRequest *aRequest = [[self fetchedResultsController] fetchRequest];

    [aRequest setPredicate:nil];

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
        // Handle error
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }  

    [self setSearchIsActive:NO];
    return;
}

然后在controllerWillChangeContent中：

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller 
{
    if ([self searchIsActive]) {
        [[[self searchDisplayController] searchResultsTableView] beginUpdates];
    }
    else  {
        [self.tableView beginUpdates];
    }
}

和controllerDidChangeContent：

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller 
{
    if ([self searchIsActive]) {
        [[[self searchDisplayController] searchResultsTableView] endUpdates];
    }
    else  {
        [self.tableView endUpdates];
    }
}

并在重置谓词时删除缓存。

希望这可以帮助。

我面临着相同的任务，并发现了解决该问题的最简单方法。 很快：您需要再定义一种方法，-fetchedResultsController与自定义复合谓词非常相似。

就我个人而言，我-fetchedResultsController看起来像这样：

- (NSFetchedResultsController *) fetchedResultsController
{
    if (fetchedResultsController != nil)
    {
        return fetchedResultsController;
    }
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Client"
                                              inManagedObjectContext:[[PTDataManager sharedManager] managedObjectContext]];
    [fetchRequest setEntity:entity];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"agency_server_id == %@", agency.server_id];
    fetchRequest.predicate = predicate;

    NSSortDescriptor *sortByName1Descriptor = [[NSSortDescriptor alloc] initWithKey:@"lastname" ascending:YES];
    NSSortDescriptor *sortByName2Descriptor = [[NSSortDescriptor alloc] initWithKey:@"firstname" ascending:YES];
    NSSortDescriptor *sortByName3Descriptor = [[NSSortDescriptor alloc] initWithKey:@"middlename" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects: sortByName1Descriptor, sortByName2Descriptor, sortByName3Descriptor, nil];

    fetchRequest.sortDescriptors = sortDescriptors;

    fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:fetchRequest managedObjectContext:[[PTDataManager sharedManager] managedObjectContext] sectionNameKeyPath:nil cacheName:nil];
    fetchedResultsController.delegate = self;
    return fetchedResultsController;
}

如您所见，我正在获取按agency.server_id谓词筛选的一家代理商的客户。结果，我也以同样的方式检索我的内容tableView（与的实现tableView和fetchedResultsController代码有关的所有内容都是非常标准的）。为了实现，searchField我定义了一个UISearchBarDelegate委托方法。我用搜索方法触发它，说-reloadTableView：

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    [self reloadTableView];
}

当然是-reloadTableView：

- (void)reloadTableView
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Client"
                                              inManagedObjectContext:[[PTDataManager sharedManager] managedObjectContext]];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sortByName1Descriptor = [[NSSortDescriptor alloc] initWithKey:@"lastname" ascending:YES];
    NSSortDescriptor *sortByName2Descriptor = [[NSSortDescriptor alloc] initWithKey:@"firstname" ascending:YES];
    NSSortDescriptor *sortByName3Descriptor = [[NSSortDescriptor alloc] initWithKey:@"middlename" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects: sortByName1Descriptor, sortByName2Descriptor, sortByName3Descriptor, nil];
    fetchRequest.sortDescriptors = sortDescriptors;

    NSPredicate *idPredicate = [NSPredicate predicateWithFormat:@"agency_server_id CONTAINS[cd] %@", agency.server_id];
    NSString *searchString = self.searchBar.text;
    if (searchString.length > 0)
    {
        NSPredicate *firstNamePredicate = [NSPredicate predicateWithFormat:@"firstname CONTAINS[cd] %@", searchString];
        NSPredicate *lastNamePredicate = [NSPredicate predicateWithFormat:@"lastname CONTAINS[cd] %@", searchString];
        NSPredicate *middleNamePredicate = [NSPredicate predicateWithFormat:@"middlename CONTAINS[cd] %@", searchString];
        NSPredicate *orPredicate = [NSCompoundPredicate orPredicateWithSubpredicates:[NSArray arrayWithObjects:firstNamePredicate, lastNamePredicate, middleNamePredicate, nil]];
        NSPredicate *andPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:idPredicate, nil]];
        NSPredicate *finalPred = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:orPredicate, andPredicate, nil]];
        [fetchRequest setPredicate:finalPred];
    }
    else
    {
        [fetchRequest setPredicate:idPredicate];
    }

    self.fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:fetchRequest managedObjectContext:[[PTDataManager sharedManager] managedObjectContext] sectionNameKeyPath:nil cacheName:nil];
    self.fetchedResultsController.delegate = self;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error])
    {
        NSLog(@"Unresolved error %@, %@", [error localizedDescription], [error localizedFailureReason]);
    }; 

    [self.clientsTableView reloadData];
}

这段代码非常类似于if-else语句中的第一个“标准” -fetchedResultsController BUT，如下所示：

+andPredicateWithSubpredicates: -使用此方法，我们可以设置一个谓词以将主要首次获取的结果保存在 tableView

+orPredicateWithSubpredicates -使用此方法，我们通过搜索查询过滤来自 searchBar

最后，我将谓词数组设置为此特定提取的复合谓词。AND为必选谓词，或OR为可选谓词。

就这样！您无需执行任何其他操作。编码愉快！

您正在使用实时搜索吗？

如果不是，则可能需要一个包含先前使用的搜索的数组（或NSFetchedResultsController），当用户按下“搜索”时，您告诉FetchedResults更改其谓词。

无论哪种方式，您都需要每次都重建FetchedResults。我建议仅使用一个NSFetchedResultsController，因为您将不得不重复很多代码，并且无需在未显示的内容上浪费内存。

只要确保您有一个NSString“ searchParameters”变量，您的FetchedResults方法就会根据需要为您重建它，并使用搜索参数（如果可用），您应该这样做：

a）将“ searchParameters”设置为某种值（如果需要所有结果，则设置为零）。

b）释放当前的NSFetchedResultsController对象并将其设置为nil。

c）重新加载表数据。

这是一个简单的代码：

- (void)searchString:(NSString*)s {
    self.searchResults = s;
    [fetchedResultsController release];
    fetchedResultsController = nil;
    [self.tableView reloadData];
}

-(NSFetchedResultsController *)fetchedResultsController {
    if (fetchedResultsController != nil) {
        return fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"EntityName" inManagedObjectContext:self.context];
    [fetchRequest setEntity:entity];

    [fetchRequest setFetchBatchSize:20];

    // searchResults is a NSString*
    if (searchResults != nil) {
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name LIKE %@",searchResults];
        [fetchRequest setPredicate:predicate];
    }

    fetchedResultsController = 
    [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
        managedObjectContext:self.context sectionNameKeyPath:nil 
        cacheName:nil];
    fetchedResultsController.delegate = self;

    [fetchRequest release];

    return fetchedResultsController;    
}

Swift 3.0，UISearchController，NSFetchedResultsController和核心数据

这段代码可以在Swift 3.0上使用Core Data！您将需要一个委托方法和几行代码来过滤和搜索模型中的对象。如果您既已实现FRC和的所有delegate方法，又将不需要任何方法searchController。

该UISearchResultsUpdating协议方法

func updateSearchResults(for searchController: UISearchController) {

    let text = searchController.searchBar.text

    if (text?.isEmpty)! {
       // Do something 
    } else {
        self.fetchedResultsController.fetchRequest.predicate = NSPredicate(format: "( someString contains[cd] %@ )", text!)
    }
    do {
        try self.fetchedResultsController.performFetch()
        self.tableView.reloadData()
    } catch {}
}

而已！希望对您有帮助！谢谢

SWIFT 3.0

使用textField时，从iOS 8开始不推荐使用UISearchDisplayController，您必须使用UISearchController。而不是与搜索控制器打交道，为什么不创建自己的搜索机制？您可以对其进行更多自定义并对其进行更多控制，而不必担心SearchController会被更改和/或弃用。

我使用的这种方法效果很好，并且不需要太多代码。但是，它确实需要使用Core Data并实现NSFetchedResultsController。

首先，创建一个TextField并使用一种方法注册它：

searchTextField?.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)

然后创建添加目标时在选择器中描述的textFieldDidChange方法：

func textFieldDidChange() {
    if let queryString = searchTextField.text {
        filterList(queryString)
        self.tableView.reloadData()
    }
}

然后，如果要filterList()使用更复杂的方法，请使用NSPredicate或NSCompound谓词在方法中过滤列表。在我的filterList方法中，我基于实体的名称和实体“ subCategories”对象的名称（一对多关系）进行过滤。

func filterList(_ queryString: String) {
    if let currentProjectID = Constants.userDefaults.string(forKey: Constants.CurrentSelectedProjectID) {
        if let currentProject = ProjectDBFacade.getProjectWithID(currentProjectID) {
            if (queryString != ""){
                let categoryPredicate = NSPredicate(format: "name CONTAINS[c] %@ && project == %@", queryString, currentProject)
                let subCategoryPredicate = NSPredicate(format: "subCategories.name CONTAINS[c] %@ && project == %@", queryString, currentProject)
                let orPredicate = NSCompoundPredicate(type: .or, subpredicates: [categoryPredicate, subCategoryPredicate])
                fetchedResultsController.fetchRequest.predicate = orPredicate
            }else{
                fetchedResultsController.fetchRequest.predicate = NSPredicate(format: "project == %@", currentProject)
            }

            do {
                try fetchedResultsController.performFetch()
            } catch {
                print("Error:  Could not fetch fetchedResultsController")
            }
        }
    }
}

我认为卢卡对此有更好的方法。请参见LargeDataSetSample和他的理由

他不使用 FetchedResultsController，而是在搜索时使用缓存，因此，当用户在SearchBar中输入更多内容时，搜索结果显示的速度会更快

我在我的应用程序中使用了他的方法，效果很好。还请记住，如果要使用Model对象，请使其尽可能简单，请参阅我关于setPropertiesToFetch的答案

这是一种处理带有多个数据集的fetchedResults的方法，既简单又通用，几乎可以应用于任何地方。存在某些情况时，只需将主要结果捕获到数组中即可。

NSArray *results = [self.fetchedResultsController fetchedObjects];

通过遍历数组或您想要的任何内容来查询数组，以创建主要fetchedResults的子集。现在，当出现某种情况时，您可以使用完整集或子集。

我真的很喜欢@Josh O'Connor的方法，因为他不使用 UISearchController。该控制器（Xcode 9）仍然存在布局错误，许多人正在尝试解决。

我确实恢复为使用a UISearchBar而不是a UITextField，并且效果很好。我对搜索/过滤器的要求是产生一个NSPredicate。这被传递给FRC：

   class ViewController: UIViewController, UITableViewDelegate, 
 UITableViewDataSource, UISearchBarDelegate {

        @IBOutlet var searchBar: UISearchBar!

         func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {

                shouldShowSearchResults = true

                if let queryString = searchBar.text {
                    filterList(queryString)

                    fetchData()
                }
            }



          func filterList(_ queryString: String) {
        if (queryString == "") {
            searchPredicate = nil
    }
        else {
            let brandPredicate = NSPredicate(format: "brand CONTAINS[c] %@", queryString)
            let modelPredicate = NSPredicate(format: "model CONTAINS[c] %@", queryString)
            let orPredicate = NSCompoundPredicate(type: .or, subpredicates: [brandPredicate, modelPredicate])
            searchPredicate = orPredicate
    }

}

...

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: filmEntity)
        request.returnsDistinctResults = true
        request.propertiesToFetch = ["brand", "model"]

        request.sortDescriptors = [sortDescriptor]
        request.predicate = searchPredicate

最后，将SearchBar连接到其委托。

我希望这可以帮助其他人

使用CoreData过滤现有UITableView的简单方法，并且已经按照您的需要进行了排序。

从字面上看，我也只有5分钟的时间来设置并开始工作。

我有一个现有的UITableView使用CoreData来自iCloud的数据填充的应用程序，它具有非常复杂的用户交互作用，我不想为重复所有操作UISearchViewController。我能够简单地FetchRequest向FetchResultsController和使用的现有谓词添加谓词，并过滤已排序的数据。

-(void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    NSPredicate *filterPredicate;

    if(searchText != nil && searchText.length > 0)
        filterPredicate = [NSPredicate predicateWithFormat:@"(someField CONTAINS[cd] %@) OR (someOtherField CONTAINS[cd] %@)", searchText, searchText];
    else
        filterPredicate = nil;

    _fetchedResultsController.fetchRequest.predicate = filterPredicate;

    NSError *error = nil;
    [_fetchedResultsController performFetch:&error];
    [self.tableView reloadData];
}