设置首选项密钥未保留iOS

Question

我正在尝试在NSUserDefaults中设置一个键。控制台日志显示当我注册默认值时设置为"YES"的密钥auto_reset_switch。但是，当我稍后读取默认值时，auto_reset_switch键为"0"。我试过将密钥设置为BOOL或NSString，但没有什么区别。我正在阅读《iOS编程大Nerd牧场指南第4版》一书中的文字。我做错了什么？

这是appDelegate.h:

    //
//  NRCAppDelegate.h
//   LifeWatch
//
//  Created by Nelson Capes on 10/13/2015.
//  Copyright © 2015 Nelson Capes. All rights reserved.
//
#import <UIKit/UIKit.h>
#import "NRCAlertView.h"
extern NSString * const NRCAutoResetSwitch;
@interface NRCAppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end

这是在appDelegate.m:中设置的密钥

    //
//  NRCAppDelegate.m
//  LifeWatch
//
//  Created by Nelson Capes on 10/13/2015.
//  Copyright © 2015 Nelson Capes. All rights reserved.
//
#import "NRCAppDelegate.h"
#import "NRCItemsViewController.h"
#import "NRCItemStore.h"
#import "NRCImageStore.h"
#import "NRCAppDelegate.h"
NSString * const NRCAutoResetSwitch = @"auto_reset_switch";
@class NRCItemsViewController;
@implementation NRCAppDelegate
+(void)initialize
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSLog(@"defaults %@", [defaults
                           dictionaryRepresentation]);
    NSDictionary *factorySettings = @{NRCAutoResetSwitch : @"YES"};
    [defaults registerDefaults:factorySettings];
    NSLog(@"defaults %@", [defaults
                           dictionaryRepresentation]);
}

这是注册默认值后的控制台日志（其中的一部分）。注意**auto_reset_switch=YES"

2016-01-12 17:23:16.088 LifeWatch[373:20370] defaults {
    NSPersonNameDefaultDisplayNameOrder = 2;
    PKEnableStockholmSettings = 1;
    "auto_reset_switch" = YES;
    "com.apple.content-rating.AppRating" = 1000;
    "com.apple.content-rating.ExplicitBooksAllowed" = 1;
    "com.apple.content-rating.ExplicitMusicPodcastsAllowed" = 1;
    "com.apple.content-rating.MovieRating" = 1000;
    "com.apple.content-rating.TVShowRating" = 1000;
}

下面是读取默认值的代码：

NSUserDefaults *defaults =[NSUserDefaults standardUserDefaults];
NSLog(@"defaults %@", [defaults
      dictionaryRepresentation]);

但现在控制台日志显示"auto_reset_switch=0"：

NSPersonNameDefaultDisplayNameOrder = 2;
PKEnableStockholmSettings = 1;
"auto_reset_switch" = 0;

Answer 1

假设您希望它是BOOL值而不是字符串值，请将@"YES"更改为@YES。这将使其成为BOOL（包装在NSNumber而不是NSString中

NSDictionary *factorySettings = @{NRCAutoResetSwitch : @YES};

Answer 2

我在stackoverflow上找到了这个答案（我不知道如何链接到它，所以我不想把这个答案归功于它。代码运行良好。

我认为OP中的示例是错误的代码。

    - (void)registerDefaultsFromSettingsBundle
{
    NSString *settingsBundle = [[NSBundle mainBundle] pathForResource:@"Settings" ofType:@"bundle"];
    if(!settingsBundle)
    {
        //NSLog(@"Could not find Settings.bundle");
        return;
    }
    NSDictionary *settings = [NSDictionary dictionaryWithContentsOfFile:[settingsBundle stringByAppendingPathComponent:@"Root.plist"]];
    NSArray *preferences = [settings objectForKey:@"PreferenceSpecifiers"];
    NSMutableDictionary *defaultsToRegister = [[NSMutableDictionary alloc] initWithCapacity:[preferences count]];
    for(NSDictionary *prefSpecification in preferences)
    {
        NSString *key = [prefSpecification objectForKey:@"Key"];
        if(key)
        {
            [defaultsToRegister setObject:[prefSpecification objectForKey:@"DefaultValue"] forKey:key];
        }
    }
    [[NSUserDefaults standardUserDefaults] registerDefaults:defaultsToRegister];
}