Ios 使用执行块正确异步获取
我继续读到，在使用核心数据时，我应该使用Ios 使用执行块正确异步获取,ios,core-data,Ios,Core Data,我继续读到，在使用核心数据时，我应该使用[\u context performBlock]：^…进行异步搜索。我一辈子都想不出的是如何订阅这个街区的结尾或完整事件。换句话说，在我的代码中，我在获取数据之前使用了UIActivityIndicatorView，并且我希望在检索数据后删除此视图。然而，我不明白如何正确地完成这一点。 在过去，我使用了dispatch\u async（dispatch\u get\u global\u queue（dispatch\u queue\u PRIORITY\
[\u context performBlock]：^…UIActivityIndicatorViewdispatch\u async（dispatch\u get\u global\u queue（dispatch\u queue\u PRIORITY\u DEFAULT，0），^{…dispatch_async(dispatch_get_main_queue(), ^(void) {
performBlock:**update**
UIActivityIndicatorView@property (strong, nonatomic) NSArray *filteredLocations;
@property (strong, nonatomic) NSArray * locationsFiltered;
//returns the search for this particular search.
- (BOOL)searchDisplayController:(UISearchDisplayController *)controller
shouldReloadTableForSearchString:(NSString *)searchString
{
if ([searchString length ]>= 3) {
[self searchForText:searchString];
return YES;
}
else{
self.filteredLocations = nil;
return NO;
}
//return YES;
}
- (void)searchForText:(NSString *)searchText
{
if (self.context && self.isSearching == FALSE)
{
//[searchController ]
//[self.searchDisplayController.searchResultsTableView.]
self.isSearching = TRUE;
NSString *predicateFormat = @"%K BEGINSWITH[cd] %@ and state ==%@";
NSString *searchAttribute = @"name";
self.filteredLocations = nil;
NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateFormat, searchAttribute, searchText,Searchstate];
[self.searchFetchRequest setPredicate:predicate];
UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
if (self.spinnerShowing ==FALSE) {
spinner.center = CGPointMake(160, 190);
spinner.hidesWhenStopped = YES;
spinner.color = [UIColor grayColor];
[self.view addSubview:spinner];
//self.spinnerShowing = ;
[spinner startAnimating];
}
[_context performBlock:^(void){
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSError *error = nil;
self.filteredLocations = [self.managedObjectContext executeFetchRequest:self.searchFetchRequest error:&error];
NSLog(@"this is how many items are in the filtered locations at this time %i", [_filteredLocations count]);
if (error)
{
NSLog(@"searchFetchRequest failed: %@",[error localizedDescription]);
}
dispatch_async(dispatch_get_main_queue(), ^(void) {
NSLog(@"stopping the spinner now.");
self.spinnerShowing = FALSE;
[spinner stopAnimating];
[spinner hidesWhenStopped];
self.isSearching = FALSE;
//self.searchDisplayController.searchResultsTableView.hidden = NO;
// [searchController reloadData];
[self.searchDisplayController.searchResultsTableView reloadData];
});
});
}];
}
}
在我开始写我的回复后，你的问题似乎有了很大的改变 让我知道这是否有用-否则我将删除，因为它不再涉及您的问题
通常，根据我的观点和经验，第二个
nsfetchedresultscoontrollerUISearchBarUISearchDisplayControllerUISearchDisplayController@界面NSFetchedResultsControllerUITableViewControllerNSMutableArray@property (nonatomic, retain) NSMutableArray *searchResults;
NSMutableArrayUITableViewControllerif (tableView == self.searchDisplayController.searchResultsTableView) {
//code for searchResultsTableView
}
然后我使用
UISearchDisplayControllerself.searchController.searchResultsTableView- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString {
// Set search predicate and filter array
if (searchString && searchString.length) {
// Your predicateFormat and searchAttribute
NSString *predicateFormat = @"%K BEGINSWITH[cd] %@ and state ==%@";
NSString *searchAttribute = @"name";
// My code
NSPredicate *searchPredicate = nil;
NSArray *fetchedObjects = nil;
NSMutableArray *arrayResults = nil;
[self.searchResults removeAllObjects];
searchPredicate = [NSPredicate predicateWithFormat:predicateFormat, searchAttribute, searchString, searchState];
fetchedObjects = self.fetchedResultsController.fetchedObjects;
arrayResults = [NSMutableArray arrayWithArray:[fetchedObjects filteredArrayUsingPredicate:searchPredicate]];
[self setSearchResults:arrayResults];
}
// Return YES to reload the search result table view
return YES;
}
UISearchDisplayController- (void)searchBarCancelButtonClicked:(UISearchBar *)searchBar {
[self setSearchResults:nil];
}
希望这能有所帮助。Andrew感谢您的回复。我将尝试一下您的解决方案。您是对的，我戏剧性地更改了我的问题。已经6个小时了，我对我的问题感到更加沮丧。然而，我最大的问题是我需要异步执行此操作。原因是我不想锁定我的主线程。你对如何正确完成这项任务有什么建议吗？非常感谢。@Miguel一些问题…1.为什么要求你进行异步搜索？2.你的搜索是否超出了
NSFetchedResultsControllerNSFetchedResultsControllerUITableViewControllerfetchedObjectNSFetchedResultsC的错误处理ontroller