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。该应用程序已经有一个 NSFetchedResultsController 和一个谓词来检索主 TableView 的数据。在更改太多代码之前，我想确保自己走在正确的道路上。我很困惑，因为很多示例都是基于数组而不是 CoreData。
这里有一些问题：
我是否需要第二个 NSFetchedResultsController 只检索匹配的项目，或者我可以使用与主 TableView 相同的一个？
如果我使用同一个，是不是像清除 FRC 缓存然后更改 handleSearchForTerm:searchString 方法中的谓词一样简单？谓词是否必须包含初始谓词以及搜索词，或者它是否记得它首先使用谓词来检索数据？
我怎样才能回到原来的结果？我只是将搜索谓词设置为 nil 吗？这不会首先杀死用于检索 FRC 结果的原始谓词吗？
如果有人有任何使用 FRC 搜索的代码示例，我将不胜感激！
我实际上只是在我的一个项目中实现了这个（你的问题和另一个错误的答案暗示了该怎么做）。我尝试了 Sergio 的回答，但在设备上实际运行时遇到了异常问题。
是的，您创建了两个获取结果控制器：一个用于正常显示，另一个用于 UISearchBar 的表格视图。
如果您只使用一个 FRC (NSFetchedResultsController)，那么原始 UITableView（不是搜索时处于活动状态的搜索表视图）可能会在您搜索时调用回调并尝试错误地使用 FRC 的过滤版本，您将看到异常抛出不正确的部分或部分中的行数。
这是我所做的：我有两个 FRC 可用作属性 fetchedResultsController 和 searchFetchedResultsController。除非有搜索，否则不应使用 searchFetchedResultsController（当搜索被取消时，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哪个适用的 FRC 中提取信息。FRC 委托方法还必须确定要更新哪个 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
在使用所有 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;
}
搜索栏的委托方法：
#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NSFetchedResultsController. 这就是我所做的，这里是详细信息。此解决方案假定您只想过滤表格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，在您的子类中定义两个属性UITableViewController（使用适当的 @synthesize 和 dealloc，如果适用）：
@property (nonatomic, retain) UISearchDisplayController *searchController;
@property (nonatomic, retain) NSString *searchString;
viewDidLoad:其次，在你的子类的方法中初始化搜索栏UITableViewController：
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，UISearchDisplayController像这样实现委托方法：
// 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方法中改变NSPredicate依赖的 if
self.searchString被定义：
-(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;
}
我花了几次尝试才使这个工作......
我理解的关键是意识到这里有两个 tableViews 在工作。一个由我的 viewcontroller 管理，一个由 searchviewcontroller 管理，然后我可以测试哪个是活动的并做正确的事情。该文档也很有帮助：
这就是我所做的 -
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。
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：
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
if ([self searchIsActive]) {
[[[self searchDisplayController] searchResultsTableView] beginUpdates];
}
else {
[self.tableView beginUpdates];
}
}
和控制器DidChangeContent：
- (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。
Swift 3.0、UISearchController、NSFetchedResultsController 和核心数据
此代码将在 Swift 3.0 上运行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。如果您已经实现了所有FRC及其delegate方法以及searchController.
协议UISearchResultsUpdating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 {}
}
就是这样！希望对你有帮助！谢谢
您是否使用实时搜索？
如果你不是，你可能想要一个数组（或 NSFetchedResultsController），其中包含你以前使用的搜索，当用户按下“搜索”时，你告诉 FetchedResults 更改其谓词。
无论哪种方式，您都需要每次都重建 FetchedResults。我建议只使用一个 NSFetchedResultsController，因为您将不得不大量重复您的代码，而且您不需要在未显示的内容上浪费内存。
只要确保您有一个 NSString "searchParameters" 变量，并且您的 FetchedResults 方法会根据需要为您重建它，使用搜索参数（如果可用），您应该这样做：
a) 将“searchParameters”设置为某个值（或 nil，如果您想要所有结果）。
b) 释放并设置为 nil 当前的 NSFetchedResultsController 对象。
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;
}
我面临同样的任务，并找到了解决它
的最简单方法。很快：-fetchedResultsController您需要再定义一种方法，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，我正在获取一个按agency.server_id谓词过滤的代理机构的客户。结果，我也在 a 中检索我的内容tableView（所有与实现相关tableView并且fetchedResultsController代码非常标准）。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，比如-reloadTableView：
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
[self reloadTableView];
}
当然还有以下定义-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];
}
这一堆代码与第一个非常相似，“标准”-fetchedResultsController 但在 if-else 语句中是：
+andPredicateWithSubpredicates:- 使用这种方法，我们可以设置一个谓词来保存我们的主要第一次获取的结果tableView
+orPredicateWithSubpredicates- 使用这种方法，我们通过搜索查询过滤现有的提取searchBar
最后，我将谓词数组设置为此特定提取的复合谓词。AND 表示必需谓词，OR 表示可选。
就这样！您无需再执行任何操作。快乐编码！
斯威夫特 3.0
使用 textField，从 iOS 8 开始不推荐使用 UISearchDisplayController，您必须使用 UISearchController。您为什么不创建自己的搜索机制，而不是处理搜索控制器？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 更改和/或被弃用。
我使用的这种方法效果很好，并且不需要太多代码。但是，它确实需要您使用 Core Data 并实现 NSFetchedResultsController。
首先，创建一个 TextField 并使用方法注册它：
searchTextField?.addTarget(self, action: #selector(textFieldDidChange), for: UIControlEvents.editingChanged)
然后创建你的 textFieldDidChange 方法，在添加目标时在选择器中描述：
func textFieldDidChange() {
if let queryString = searchTextField.text {
filterList(queryString)
self.tableView.reloadData()
}
}
filterList()然后，如果它更复杂，您想使用 NSPredicate 或 NSCompound 谓词过滤方法中的列表。在我的 filterList 方法中，我根据实体的名称和实体“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 Luka 对此有更好的方法。见LargeDataSetSample和他的理由
他不使用FetchedResultsController，但在搜索时使用缓存，因此当用户在 SearchBar 中键入更多内容时，搜索结果会显示得更快
我在我的应用程序中使用了他的方法，它工作正常。还请记住，如果您想使用 Model 对象，请使其尽可能简单，请参阅我关于setPropertiesToFetch的回答
这是一种处理具有多个数据集的 fetchedResults 的方法，该方法既简单又通用，几乎可以应用于任何地方。当某些条件存在时，只需将您的主要结果抓取到一个数组中。
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，当某些条件存在时，您可以使用完整集或子集。
我真的很喜欢@Josh O'Connor 不使用UISearchController. 这个控制器（Xcode 9）仍然存在许多人试图解决的布局错误。
我确实恢复使用 aUISearchBar而不是 a UITextField，并且效果很好。我对搜索/过滤器的要求是生成一个NSPredicate. 这将传递给 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 连接到它的委托。
我希望这对其他人有帮助
使用 CoreData 过滤现有 UITableView 的简单方法，并且已经按您想要的方式排序。
从字面上看，这对我来说也有 5 分钟的时间来设置和开始工作。
我有一个现有的UITableViewusingCoreData填充了来自 iCloud 的数据，它具有非常复杂的用户交互，我不想为UISearchViewController. 我能够简单地添加一个谓词到现有的FetchRequest已经使用的FetchResultsController并且过滤已经排序的数据。
-(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];
}