ios - 我的应用程序中的 NSFetchedResultsControllerDelegate 警告

Question

我在 Xcode 收到以下警告，但不知道原因。欢迎任何帮助。

 Assigning to 'id<NSFetchedResultsControllerDelegate>' from incompatible type 'CollapsableTableViewViewController *'

这是我的代码，警告在标有注释的行处引发。

#import "CollapsableTableViewViewController.h"
#import "CollapsableTableView.h"
#import "CollapsableTableViewAppDelegate.h"


@interface CollapsableTableViewViewController()

@end


@implementation CollapsableTableViewViewController
@synthesize fetchedResultsController = _fetchedResultsController;

@synthesize managedObjectContext;
/*
// The designated initializer. Override to perform setup that is required before the view is loaded.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
    //1
    CollapsableTableViewAppDelegate* appDelegate = [UIApplication sharedApplication].delegate;
    //2
    self.managedObjectContext = appDelegate.managedObjectContext;


      self.fetchedResultsController = nil;









    CollapsableTableView* tableView = (CollapsableTableView*) myTableView;
    tableView.collapsableTableViewDelegate = self;

//    [tableView setIsCollapsed:YES forHeaderWithTitle:@"First Section"];
//    [tableView setIsCollapsed:YES forHeaderWithTitle:@"Second Section"];
//    [tableView setIsCollapsed:YES forHeaderWithTitle:@"Third Section"];
//    [tableView setIsCollapsed:YES forHeaderWithTitle:@"Fourth Section"];
//    [tableView setIsCollapsed:YES forHeaderWithTitle:@"Fifth Section"];
}


// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return YES;
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    [spinner release];
    spinner = nil;
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}


- (void)dealloc {
    [spinner release];
    [super dealloc];
}


#pragma mark -
#pragma mark UITableViewDataSource

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 6;
}


+ (NSString*) titleForHeaderForSection:(int) section
{
    switch (section)
    {
        case 0 : return @"Overdue";
        case 1 : return @"Today";
        case 2 : return @"Tomorrow";
        case 3 : return @"Upcoming";
        case 4 : return @"Someday";
        case 5 : return @"Completed";
        //default : return [NSString stringWithFormat:@"Section no. %i",section + 1];
    }
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    return [CollapsableTableViewViewController titleForHeaderForSection:section];
}

// Uncomment the following two methods to use custom header views.
//- (UILabel *) createHeaderLabel: (UITableView *) tableView :(NSString *)headerTitle {
//    UILabel *titleLabel = [[[UILabel alloc] initWithFrame:CGRectZero] autorelease];
//    titleLabel.frame =CGRectMake(0, 0, tableView.frame.size.width - 20, 60);
//    titleLabel.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin;
//    titleLabel.backgroundColor = [UIColor clearColor];
//    titleLabel.textColor = [UIColor whiteColor];
//    titleLabel.font=[UIFont fontWithName:@"Helvetica-Bold" size:20];
//    titleLabel.text = headerTitle;
//    titleLabel.textAlignment = UITextAlignmentRight;
//    return titleLabel;
//}
//
//- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
//{
//    // create the parent view that will hold header Label
//    UIView * customView = [[[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, tableView.frame.size.width , 60)]autorelease];
//    UILabel *titleLabel;
//    titleLabel = [self createHeaderLabel: tableView :[CollapsableTableViewViewController titleForHeaderForSection:section]];
//    
//    [customView addSubview:titleLabel];
//    
//    UILabel* collapsedLabel = [[[UILabel alloc] initWithFrame:CGRectMake(10,0,50,60)] autorelease];
//    collapsedLabel.autoresizingMask = UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin;
//    collapsedLabel.backgroundColor = [UIColor clearColor];
//    collapsedLabel.textColor = [UIColor whiteColor];
//    collapsedLabel.text = @"-";
//    collapsedLabel.tag = COLLAPSED_INDICATOR_LABEL_TAG;
//    [customView addSubview:collapsedLabel];
//    
//    customView.tag = section;
//    customView.backgroundColor = [UIColor blackColor];
//    return customView;
//}

//- (NSString*) tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section
//{
//    return [NSString stringWithFormat:@"Footer %i",section + 1];
//}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    int numero = [[self.fetchedResultsController sections] count];
    NSLog(@"numero = %d", numero);
    switch (section)
    {
        case 2 : return numero;
        case 3 : return 30;
        default : return 8;
    }
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) 
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }

    // Configure the cell.

    switch (indexPath.row)
    {
        case 0 : cell.textLabel.text = @"First Cell"; break;
        case 1 : cell.textLabel.text = @"Second Cell"; break;
        case 2 : cell.textLabel.text = @"Third Cell"; break;
        case 3 : cell.textLabel.text = @"Fourth Cell"; break;
        case 4 : cell.textLabel.text = @"Fifth Cell"; break;
        case 5 : cell.textLabel.text = @"Sixth Cell"; break;
        case 6 : cell.textLabel.text = @"Seventh Cell"; break;
        case 7 : cell.textLabel.text = @"Eighth Cell"; break;
        default : cell.textLabel.text = [NSString stringWithFormat:@"Cell %i",indexPath.row + 1];
    }

    //cell.detailTextLabel.text = ...;

    return cell;
}


#pragma mark -
#pragma mark CollapsableTableViewDelegate

- (void) collapsableTableView:(CollapsableTableView*) tableView willCollapseSection:(NSInteger) section title:(NSString*) sectionTitle headerView:(UIView*) headerView
{
    [spinner startAnimating];
}

- (void) collapsableTableView:(CollapsableTableView*) tableView didCollapseSection:(NSInteger) section title:(NSString*) sectionTitle headerView:(UIView*) headerView
{
    [spinner stopAnimating];
}

- (void) collapsableTableView:(CollapsableTableView*) tableView willExpandSection:(NSInteger) section title:(NSString*) sectionTitle headerView:(UIView*) headerView
{
    [spinner startAnimating];
}

- (void) collapsableTableView:(CollapsableTableView*) tableView didExpandSection:(NSInteger) section title:(NSString*) sectionTitle headerView:(UIView*) headerView
{
    [spinner stopAnimating];
}


#pragma mark -
#pragma mark IBAction methods

- (IBAction) toggleSection2
{
    NSString* sectionTitle = //[NSString stringWithFormat:@"Tag %i",1]; // Use this expression when using custom header views.
        [CollapsableTableViewViewController titleForHeaderForSection:1]; // Use this expression when specifying text for headers.
    CollapsableTableView* collapsableTableView = (CollapsableTableView*) myTableView;
    BOOL isCollapsed = [[collapsableTableView.headerTitleToIsCollapsedMap objectForKey:sectionTitle] boolValue];
    [collapsableTableView setIsCollapsed:! isCollapsed forHeaderWithTitle:sectionTitle];
}

- (NSFetchedResultsController *)fetchedResultsController {

    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

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

    NSSortDescriptor *sort = [[NSSortDescriptor alloc]
                              initWithKey:@"tdText" ascending:NO];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

    [fetchRequest setFetchBatchSize:20];

    NSFetchedResultsController *theFetchedResultsController =
    [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                        managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil
                                                   cacheName:nil];
    self.fetchedResultsController = theFetchedResultsController;
    _fetchedResultsController.delegate = self; //the warning is on this line

    return _fetchedResultsController;

}



@end

这是我的头文件:

#import <UIKit/UIKit.h>
#import "CollapsableTableViewDelegate.h"


@interface CollapsableTableViewViewController : UIViewController <UITableViewDelegate,UITableViewDataSource,CollapsableTableViewDelegate>
{
    IBOutlet UITableView* myTableView;
    IBOutlet UIActivityIndicatorView *spinner;


}

@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;

- (IBAction) toggleSection2;


@end

Answer 1

更换@interface点 m​​ 文件中带有 @interface CollapsableTableViewViewController() <NSFetchedResultsControllerDelegate> 的行解决你的问题。

你必须告诉 fetchedResultsController “嘿，这个类符合 NSFetchedResultsControllerDelegate 协议(protocol)”。