如何将默认条目添加到我的字典中，以便在首次运行时不会为空

Question

我需要一些帮助，试图在bandsDictionary中插入几个默认条目，以便在用户添加新条目之前它不为空。

// TableViewController.h 

#import <UIKit/UIKit.h>

@class WBABand, WBABandDetailsViewController;
@interface WBABandsListTableViewController : UITableViewController

@property (nonatomic, strong) NSMutableDictionary *bandsDictionary;
@property (nonatomic, strong) NSMutableArray *firstLettersArray;

@property (nonatomic, strong) WBABandDetailsViewController *bandInfoViewController;

//NSMutableDictionary *tempDictionary;
@property (nonatomic, retain) NSMutableDictionary *tempDictionary;

-(void)addNewBand:(WBABand*)bandObject;

-(void)saveBandsDictionary;

-(void)loadBandsDictionary;

-(void)deleteBandAtIndexPath:(NSIndexPath*)indexPath;

-(void)updateBandObject:(WBABand*)bandObject atIndexPath:(NSIndexPath*)indexPath;

-(IBAction)addBandTouched:(id)sender;

@end



//TableViewController.m


#import "WBABandsListTableViewController.h"
#import "WBABand.h"
#import "WBABandDetailsViewController.h"

static NSString *bandsDictionarytKey = @"BABandsDictionarytKey";

@interface WBABandsListTableViewController ()

@end

@implementation WBABandsListTableViewController

-(id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

-(void)viewDidLoad
{
    [super viewDidLoad];

    [self loadBandsDictionary];

    self.navigationItem.rightBarButtonItem = self.editButtonItem;
    self.clearsSelectionOnViewWillAppear = NO;
}

-(void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return self.bandsDictionary.count;
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    NSString *firstLetter = [self.firstLettersArray objectAtIndex:section];
    NSMutableArray *bandsForLetter = [self.bandsDictionary objectForKey:firstLetter];
    return bandsForLetter.count;
}

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

    NSString *firstLetter = [self.firstLettersArray objectAtIndex:indexPath.section];
    NSMutableArray *bandsForLetter = [self.bandsDictionary objectForKey:firstLetter];
    WBABand *bandObject = [bandsForLetter objectAtIndex:indexPath.row];

    // Configure the cell...
    cell.textLabel.text = bandObject.name;

    return cell;
}

- (void)addNewBand:(WBABand*)bandObject
{
    NSString *bandNameFirstLetter = [bandObject.name substringToIndex:1];
    NSMutableArray *bandsForLetter = [self.bandsDictionary objectForKey:bandNameFirstLetter];

    if(!bandsForLetter)
        bandsForLetter = [NSMutableArray array];

    [bandsForLetter addObject:bandObject];
    [bandsForLetter sortUsingSelector:@selector(compare:)];
    [self.bandsDictionary setObject:bandsForLetter forKey:bandNameFirstLetter];

    if(![self.firstLettersArray containsObject:bandNameFirstLetter])
    {
        [self.firstLettersArray addObject:bandNameFirstLetter];
        [self.firstLettersArray sortUsingSelector:@selector(compare:)];
    }

    [self saveBandsDictionary];
}

- (void)saveBandsDictionary
{
    NSData *bandsDictionaryData = [NSKeyedArchiver archivedDataWithRootObject:self.bandsDictionary];
    [[NSUserDefaults standardUserDefaults] setObject:bandsDictionaryData forKey:bandsDictionarytKey];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

- (void)loadBandsDictionary
{
    NSData *bandsDictionaryData = [[NSUserDefaults standardUserDefaults] objectForKey:bandsDictionarytKey];

    if(bandsDictionaryData)
    {
        self.bandsDictionary = [NSKeyedUnarchiver unarchiveObjectWithData:bandsDictionaryData];
        self.firstLettersArray = [NSMutableArray arrayWithArray:self.bandsDictionary.allKeys];
        [self.firstLettersArray sortUsingSelector:@selector(compare:)];
    }
    else
    {
        self.bandsDictionary = [NSMutableDictionary dictionary];
        self.firstLettersArray = [NSMutableArray array];
    }
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    if(self.bandInfoViewController)
    {
        NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];

        if(self.bandInfoViewController.saveBand)
        {
            if(selectedIndexPath)
            {
                [self updateBandObject:self.bandInfoViewController.bandObject atIndexPath:selectedIndexPath];
                [self.tableView deselectRowAtIndexPath:selectedIndexPath animated:YES];
            }
            else
                [self addNewBand:self.bandInfoViewController.bandObject];
            [self.tableView reloadData];
        }
        else if (selectedIndexPath)
        {
            [self deleteBandAtIndexPath:selectedIndexPath];
        }

        self.bandInfoViewController = nil;
    }
}

- (IBAction)addBandTouched:(id)sender
{
    UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    self.bandInfoViewController = (WBABandDetailsViewController *)[sb instantiateViewControllerWithIdentifier:@"bandDetails"];

    [self presentViewController:self.bandInfoViewController animated:YES completion:nil];
}

- (NSString*)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    return [self.firstLettersArray objectAtIndex:section];
}

- (NSArray*)sectionIndexTitlesForTableView:(UITableView *)tableView
{
    return self.firstLettersArray;
}

- (int)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index
{
    return [self.firstLettersArray indexOfObject:title];
}

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete)
    {
        [self deleteBandAtIndexPath:indexPath];
    }
}

- (void)deleteBandAtIndexPath:(NSIndexPath*)indexPath
{
    NSString *sectionHeader = [self.firstLettersArray objectAtIndex:indexPath.section];
    NSMutableArray *bandsForLetter = [self.bandsDictionary objectForKey:sectionHeader];
    [bandsForLetter removeObjectAtIndex:indexPath.row];

    if(bandsForLetter.count == 0)
    {
        [self.firstLettersArray removeObject:sectionHeader];
        [self.bandsDictionary removeObjectForKey:sectionHeader];
        [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:UITableViewRowAnimationFade];
    }
    else
    {
        [self.bandsDictionary setObject:bandsForLetter forKey:sectionHeader];
        [self.tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }

    [self saveBandsDictionary];
}

- (void)updateBandObject:(WBABand*)bandObject atIndexPath:(NSIndexPath*)indexPath
{
    NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
    NSString *sectionHeader = [self.firstLettersArray objectAtIndex:selectedIndexPath.section];
    NSMutableArray *bandsForSection = [self.bandsDictionary objectForKey:sectionHeader];
    [bandsForSection removeObjectAtIndex:indexPath.row];
    [bandsForSection addObject:bandObject];
    [bandsForSection sortUsingSelector:@selector(compare:)];
    [self.bandsDictionary setObject:bandsForSection forKey:sectionHeader];
    [self saveBandsDictionary];
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSIndexPath *selectedIndexPath = [self.tableView indexPathForSelectedRow];
    NSString *sectionHeader = [self.firstLettersArray objectAtIndex:selectedIndexPath.section];
    NSMutableArray *bandsForSection = [self.bandsDictionary objectForKey:sectionHeader];
    WBABand *bandObject = [bandsForSection objectAtIndex:selectedIndexPath.row];
    self.bandInfoViewController = segue.destinationViewController;
    self.bandInfoViewController.bandObject = bandObject;
    self.bandInfoViewController.saveBand = YES;
}

@end

Answer 1

您可以在loadBandsDictionary的else子句中添加一些band对象，然后保存用户默认值。你还没有提供你的WBABand课程，所以我不知道所有的属性，但它会是这样的 -

- (void)loadBandsDictionary
{
    NSData *bandsDictionaryData = [[NSUserDefaults standardUserDefaults] objectForKey:bandsDictionarytKey];

    if(bandsDictionaryData)
    {
        self.bandsDictionary = [NSKeyedUnarchiver unarchiveObjectWithData:bandsDictionaryData];
        self.firstLettersArray = [NSMutableArray arrayWithArray:self.bandsDictionary.allKeys];
        [self.firstLettersArray sortUsingSelector:@selector(compare:)];
    }
    else
    {
        self.bandsDictionary = [NSMutableDictionary dictionary];
        self.firstLettersArray = [NSMutableArray array];
        WBABand *sampleBand=[[WBABand alloc]init];
        sampleBand.name=@"The Smashing Beatles";
        //Set other band properties;
        [self addNewBand:sampleBand];
        WBABand *secondSampleBand=[[WBABand alloc]init]
        secondSampleBand.name=@"Nine Inch Screws";
        [self addNewBand:secondSampleBand];
    }
}