Ios 通过更改其他视图中的设置来搜索NSFetchedResults

我已经阅读了很多内容，并观看了一些关于如何使用搜索栏搜索核心数据的教程，但是我还没有看到任何关于如何通过将设置从

Settings

视图传递到

Table view

来更改排序描述符的内容

我有一个

search

bar按钮项，按下该项时，它会转到

search设置svc

。视图通过将布尔值从一个VC传递到另一个VC进行通信，反之亦然。问题是，通过更改TableVC顺序，表没有相应地对应（我尝试调用self.tableview beginUpdates、self.tableview reload、self-fetchedResultsController等）

重点是对TableVC结果重新排序，而不是像谓词那样只显示特定的结果

我为SettingsVC创建了一个委托，这样我就可以将布尔值传递给SettingsVC，如果有任何更改，SettingsVC就可以返回不同的更改值

问题是，我无法设法更新表视图（甚至无法预捕获已获取的结果）

以下是我的

-（NSFetchedResultsController*）fetchedResultsController

方法的代码：

// return if already initialized
if (self.fetchedResultsController != nil) {
    return self.fetchedResultsController;
}

if (dateSearch == true){

    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

    // the entity to fetch
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Details" inManagedObjectContext:managedObjectContext];
    // how to sort the data
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"addDate" ascending:YES];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entity];
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                                                         managedObjectContext:managedObjectContext
                                                                           sectionNameKeyPath:nil
                                                                                    cacheName:nil];

    // fetch the data
    NSError *e = nil;
    if (![self.fetchedResultsController performFetch:&e]) {
        NSLog(@"fetch error(Date): %@", e );
        abort();
    }

    NSLog(@"Dates loaded");
}

if (mostAmount == true){

    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

    // the entity to fetch
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Details" inManagedObjectContext:managedObjectContext];
    // how to sort the data
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"amount" ascending:NO];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entity];
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                                                         managedObjectContext:managedObjectContext
                                                                           sectionNameKeyPath:nil
                                                                                    cacheName:nil];

    // fetch the data
    NSError *e = nil;
    if (![self.fetchedResultsController performFetch:&e]) {
        NSLog(@"fetch error (Most Fuel): %@", e);
        abort();
    }

    NSLog(@"Amount loaded");

}

else{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

    // the entity to fetch
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Details" inManagedObjectContext:managedObjectContext];
    // how to sort the data
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"addDate" ascending:YES];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entity];
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                                                        managedObjectContext:managedObjectContext
                                                                          sectionNameKeyPath:nil
                                                                                   cacheName:nil];

    // fetch the data
    NSError *e = nil;
    if (![self.fetchedResultsController performFetch:&e]) {
        NSLog(@"fetch error(Date): %@", e );
        abort();
    }

    NSLog(@"Defualt loaded");
}

return self.fetchedResultsController;

我需要一个默认值，因为在开始时，当我将TableVC中的布尔值初始化为false时，当我转到我的设置VC时，可以更新它们

我的SearchSettingsVC具有UI开关，可将值从true更改为false（反之亦然），从而成功更新表VC中的等效布尔值，如我返回SearchSettingsVC时所示

我的

prepareForSegue

表格中的代码

if ([[segue identifier] isEqualToString:@"searchSettings"]){
    //pass new search settings in here
    SearchSelectionSettings * settingsVC = (SearchSelectionSettings *)segue.destinationViewController;

    settingsVC.delegate = self;
    settingsVC.dateSearch = dateSearch;
    settingsVC.mostAmount = mostAmount;    

#pragma mark - SettingsViewControllerDelegate methods
//record the settings changed in the settings view
//dismissViewController changes the screen
- (void)closeSettings:(id)sender {

    NSLog(@"Working?");

    dateSearch = ((SearchSelectionSettings *)sender).dateSearch;
    mostAmount = ((SearchSelectionSettings *)sender).mostAmount;


     [self dismissViewControllerAnimated:YES completion:nil];
     [self FetchedResultsController];
     NSIndexPath * indexPath;
    [self tableView:self.tableView cellForRowAtIndexPath:indexPath];
}

这是我的closeSettings方法，它位于我的TableVC中

if ([[segue identifier] isEqualToString:@"searchSettings"]){
    //pass new search settings in here
    SearchSelectionSettings * settingsVC = (SearchSelectionSettings *)segue.destinationViewController;

    settingsVC.delegate = self;
    settingsVC.dateSearch = dateSearch;
    settingsVC.mostAmount = mostAmount;    

#pragma mark - SettingsViewControllerDelegate methods
//record the settings changed in the settings view
//dismissViewController changes the screen
- (void)closeSettings:(id)sender {

    NSLog(@"Working?");

    dateSearch = ((SearchSelectionSettings *)sender).dateSearch;
    mostAmount = ((SearchSelectionSettings *)sender).mostAmount;


     [self dismissViewControllerAnimated:YES completion:nil];
     [self FetchedResultsController];
     NSIndexPath * indexPath;
    [self tableView:self.tableView cellForRowAtIndexPath:indexPath];
}

---

将布尔值从一个VC传递到另一个VC非常有效。根据fetchedResults

语句更新TableView如果

语句没有更新，则SettingsVC中的my开关每次都会更新，不会出现任何问题。有人可以提供帮助或推荐教程吗？

fetchedResultscontrollergetter的开头几行，即：

// return if already initialized
if (self.fetchedResultsController != nil) {
    return self.fetchedResultsController;
}

这意味着，一旦创建了fetchedResultsController，访问它时将不会执行其余代码。因此，解决问题的快速方法是在

closeSettings

方法中将

self.fetchedResultsController

设置为

nil

，然后重新加载表视图。当tableview重新加载时，它将再次访问

fetchedResultsController

，由于它现在是

nil

，上述代码将被绕过并使用您的代码

#pragma mark - SettingsViewControllerDelegate methods
//record the settings changed in the settings view
//dismissViewController changes the screen
- (void)closeSettings:(id)sender {

    NSLog(@"Working?");

    dateSearch = ((SearchSelectionSettings *)sender).dateSearch;
    mostAmount = ((SearchSelectionSettings *)sender).mostAmount;


    [self dismissViewControllerAnimated:YES completion:nil];
    self.fetchedResultsController = nil;
    [self.tableView reloadData];
}

或者，您可以修改fetchedResultsController的fetch，然后让它重新形成fetch：

#pragma mark - SettingsViewControllerDelegate methods
//record the settings changed in the settings view
//dismissViewController changes the screen
- (void)closeSettings:(id)sender {

    NSLog(@"Working?");

    dateSearch = ((SearchSelectionSettings *)sender).dateSearch;
    mostAmount = ((SearchSelectionSettings *)sender).mostAmount;


    [self dismissViewControllerAnimated:YES completion:nil];
    NSFetchRequest *request = [[NSFetchRequest fetchRequestWithEntityName:@"Details"];
    NSSortDescriptor *sort;
    if (dateSearch == true){
        sort = [NSSortDescriptor sortDescriptorWithKey:@"addDate" ascending:YES];
        NSLog(@"Dates loaded");
    } else if (mostAmount == true) {
        sort = [NSSortDescriptor sortDescriptorWithKey:@"amount" ascending:NO];
        NSLog(@"Amount loaded");
    } else {
        sort = [NSSortDescriptor sortDescriptorWithKey:@"addDate" ascending:YES];
        NSLog(@"Default loaded");
    }
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];
    self.fetchedResultsController.fetchRequest = request;
    // fetch the data
    NSError *e = nil;
    if (![self.fetchedResultsController performFetch:&e]) {
        NSLog(@"fetch error (Most Fuel): %@", e);
        abort();
    }
    [self.tableView reloadData];
}

---

这样，您就可以简化fetchedResultsController代码，使其只加载默认值。

如果我遇到您，我将很乐意为您购买饮料，原因如下：1。你的答案中的解决方案2奏效了。2.您给出了一个答案，并用代码进行了解释和演示（我发现这两者的结合并不常见，人们只是简单地给出了一个措辞明确的答案，而没有一个有效的答案）。3.你回答了很多相关的建议。非常感谢。