一. 偏好存儲使用場景

• 用戶存儲偏好設置
• 緩存信息
• 輕量級數(shù)據存儲
• 不可用于存儲大量數(shù)據
• 不要濫用synchronize方法
• 警惕數(shù)據被清空袋坑，因為NSUserDefaults是單例類褒颈，代碼的任何地方都可以將它刪除

二. 偏好存儲工作原理

三. 偏好存儲支持的數(shù)據類型

不可存儲可變類型

不可存儲可變類

四. 偏好存儲的增加、讀取瞧掺、修改纹腌、刪除

//
//  ViewController.m
//  UserDefaultDemo


#import "ViewController.h"

@interface ViewController ()
- (IBAction)addPreference:(id)sender;
- (IBAction)readPreference:(id)sender;
- (IBAction)modifyPreference:(id)sender;
- (IBAction)deletePreference:(id)sender;
- (IBAction)clearAllPreference:(id)sender;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}


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


- (IBAction)addPreference:(id)sender {
    //增加偏好設置
    //獲取NSUserDefault類實例
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    //存儲數(shù)字類型
    [userDefaults setBool:NO forKey:@"BoolKey"];
    [userDefaults setInteger:123 forKey:@"IntegerKey"];
    [userDefaults setFloat:0.123 forKey:@"FloatKey"];
    [userDefaults setDouble:0.123456 forKey:@"DoubleKey"];
    //存儲字符串類型
    [userDefaults setObject:@"Hello" forKey:@"StringKey"];
    //存儲NSData類型
    NSData *data = [@"hello Data" dataUsingEncoding:NSUTF8StringEncoding];
    [userDefaults setObject:data forKey:@"DataKey"];
    //存儲數(shù)組類型
    NSArray *array = @[@"one",@"two",@"three"];
    [userDefaults setObject:array forKey:@"ArrayKey"];
    //存儲字典類型
    NSDictionary *dict = @{@"key1":@"value1",@"key2":@"value2",@"key3":@"value3"};
    [userDefaults setObject:dict forKey:@"DictionaryKey"];
    
    [userDefaults synchronize];//將存儲的偏好存儲內容同步到ROM中
}

- (IBAction)readPreference:(id)sender {
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    //讀取數(shù)字值
    BOOL readBool = [userDefaults boolForKey:@"BoolKey"];
    NSLog(@"Bool value is:%@",readBool?@"YES":@"NO");
    
    NSInteger readInteger = [userDefaults integerForKey:@"IntegerKey"];
    NSLog(@"Integer value is:%ld",readInteger);
    
    float readFloat = [userDefaults floatForKey:@"FloatKey"];
    NSLog(@"Float value is:%f",readFloat);
    
    double readDouble = [userDefaults doubleForKey:@"DoubleKey"];
    NSLog(@"Double value is:%lf",readDouble);
    
    //讀取字符串值
    NSString* readString = [userDefaults objectForKey:@"StringKey"];
    NSLog(@"String value is:%@",readString);
    
    //讀取NSData值
    NSData* readData = [userDefaults objectForKey:@"NSDataKey"];
    NSString* dataToString = [[NSString alloc]initWithData:readData encoding:NSUTF8StringEncoding];
    NSLog(@"NSData value is:%@",dataToString);
    //讀取數(shù)組值
    NSArray* readArray = [userDefaults objectForKey:@"ArrayKey"];
    NSLog(@"Array value is:%@",readArray);
    //讀取字典值
    NSDictionary* readDictionary = [userDefaults objectForKey:@"DictionaryKey"];
    NSLog(@"Dictionary value is:%@",readDictionary);
}

- (IBAction)modifyPreference:(id)sender {
    //修改偏好設置 修改和增加其實是一樣的
    //獲取NSUserDefault類實例
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    //更新數(shù)字類型
    [userDefaults setBool:YES forKey:@"BoolKey"];
    [userDefaults setInteger:456 forKey:@"IntegerKey"];
    [userDefaults setFloat:3.14 forKey:@"FloatKey"];
    [userDefaults setDouble:9.87654 forKey:@"DoubleKey"];
    //更新字符串類型
    [userDefaults setObject:@"World" forKey:@"StringKey"];
    //更新NSData類型
    NSData *data = [@"new Data" dataUsingEncoding:NSUTF8StringEncoding];
    [userDefaults setObject:data forKey:@"DataKey"];
    //更新數(shù)組類型
    NSArray *array = @[@"four",@"five",@"six"];
    [userDefaults setObject:array forKey:@"ArrayKey"];
    //更新字典類型
    NSDictionary *dict = @{@"key5":@"value5",@"key6":@"value6",@"key7":@"value7"};
    [userDefaults setObject:dict forKey:@"DictionaryKey"];
    
    [userDefaults synchronize];//將存儲的偏好存儲內容同步到ROM中
}

- (IBAction)deletePreference:(id)sender {
    //獲取NSUserDefaults實例
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    
    //存儲數(shù)字值
    [userDefaults removeObjectForKey:@"BoolKey"];
    [userDefaults removeObjectForKey:@"IntegerKey"];
    [userDefaults removeObjectForKey:@"FloatKey"];
    [userDefaults removeObjectForKey:@"DoubleKey"];
    //存儲字符串值
    [userDefaults removeObjectForKey:@"StringKey"];
    //存儲NSData值
    [userDefaults removeObjectForKey:@"NSDataKey"];
    //存儲數(shù)組值
    [userDefaults removeObjectForKey:@"ArrayKey"];
    //存儲字典值
    [userDefaults removeObjectForKey:@"DictionaryKey"];
    
    //同步數(shù)據
    [userDefaults synchronize];
}

- (IBAction)clearAllPreference:(id)sender {
    //刪除所有偏好存儲
    //獲得應用的域的字符串
    NSString *appDomainString = [[NSBundle mainBundle]bundleIdentifier];
    //清空偏好存儲
    [[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomainString];
}
@end

五. 案例——緩存設置頁面

//
//  ViewController.m
//  SettingDemo

#import "ViewController.h"

@interface ViewController ()<UITextFieldDelegate>
@property (weak, nonatomic) IBOutlet UITextField *myTextField;
@property (weak, nonatomic) IBOutlet UISwitch *mySwitch;
- (IBAction)switchAction:(UISwitch *)sender;
@property (weak, nonatomic) IBOutlet UISlider *mySlider;
- (IBAction)sliderAction:(UISlider *)sender;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _myTextField.delegate = self;
    [self loadPreference];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
//加載偏好存儲的值
- (void)loadPreference {
    NSString *string = [[NSUserDefaults standardUserDefaults]objectForKey:@"textKey"];
    _myTextField.text = string;
    
    BOOL switchValue = [[NSUserDefaults standardUserDefaults]boolForKey:@"switchKey"];
    _mySwitch.on = switchValue;
    
    float sliderValue = [[NSUserDefaults standardUserDefaults]floatForKey:@"sliderKey"];
    _mySlider.value = sliderValue;
}

- (void)textFieldDidEndEditing:(UITextField *)textField {
    NSLog(@"字符串變?yōu)椋?@",textField.text);
    //存儲/更新字符串的值
    [[NSUserDefaults standardUserDefaults] setObject:textField.text forKey:@"textKey"];
    //更新偏好存儲到ROM中
    [[NSUserDefaults standardUserDefaults]synchronize];
}

- (IBAction)switchAction:(UISwitch *)sender {
    NSLog(@"開關變?yōu)椋?d",sender.isOn);
    //存儲/更新開關的值
    [[NSUserDefaults standardUserDefaults] setBool:sender.isOn forKey:@"switchKey"];
    [[NSUserDefaults standardUserDefaults]synchronize];
    
}
- (IBAction)sliderAction:(UISlider *)sender {
    NSLog(@"滑塊位置：%f",sender.value);
    //存儲/更新滑塊的值
    [[NSUserDefaults standardUserDefaults] setFloat:sender.value forKey:@"sliderKey"];
    [[NSUserDefaults standardUserDefaults]synchronize];
}

//隱藏鍵盤
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self.view endEditing:YES];
}
@end