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IOS中NSUserDefaults的用法(轻量级本地数据存储)

    博客分类:
  • IOS
 
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NSUserDefaults适合存储轻量级的本地数据,比如要保存一个登陆界面的数据,用户名、密码之类的,个人觉得使用NSUserDefaults是首选。下次再登陆的时候就可以直接从NSUserDefaults里面读取上次登陆的信息咯。

因为如果使用自己建立的plist文件什么的,还得自己显示创建文件,读取文件,很麻烦,而是用NSUserDefaults则不用管这些东西,就像读字符串一样,直接读取就可以了。

NSUserDefaults支持的数据格式有:NSNumber(Integer、Float、Double),NSString,NSDate,NSArray,NSDictionary,BOOL类型。很实用吧

NSUserDefaults很方便,读取也很容易。下面给出一个示例看看如何使用:(PS:更详细的也可以参考官方文档哈)

ViewController.h文件中主要是放几个控件,用于显示存储的数据:


[cpp]
 #import <UIKit/UIKit.h> 
 
@interface ViewController : UIViewController 

     
    IBOutlet UILabel *txtInteger; 
    IBOutlet UILabel *txtFloat; 
    IBOutlet UILabel *txtDouble; 
    IBOutlet UILabel *txtNSString; 
    IBOutlet UILabel *txtNSDate; 
    IBOutlet UILabel *txtNSArray; 
    IBOutlet UILabel *txtNSDictionary; 

 
@end 
ViewController.m文件中最重要的是两个方法:

saveNSUserDefaults:用于将各种类型数据保存到NSUserDefaults中


readNSUserDefautls:用于从NSUserDefaults中读取各种类型的数据。在viewDidLoad中调用这两个方法就可以看出结果咯


[cpp]
#import "ViewController.h" 
 
@interface ViewController () 
 
@end 
 
@implementation ViewController 
 
- (void)viewDidLoad 

    [super viewDidLoad]; 
 
    [self saveNSUserDefaults];  //调用此方法将各种数据存储到NSUserDefautls中,在下面定义 
    [self readNSUserDefaults];  //调用此方法从NSUserDefautls中读取各种数据,在下面定义 

 
- (void)viewDidUnload 

    [txtNSString release]; 
    txtNSString = nil; 
    [txtNSDate release]; 
    txtNSDate = nil; 
    [txtNSArray release]; 
    txtNSArray = nil; 
    [txtNSDictionary release]; 
    txtNSDictionary = nil; 
    [txtInteger release]; 
    txtInteger = nil; 
    [txtFloat release]; 
    txtFloat = nil; 
    [txtDouble release]; 
    txtDouble = nil; 
    [super viewDidUnload]; 
    // Release any retained subviews of the main view. 

 
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation 

    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown); 

 
- (void)dealloc { 
    [txtNSString release]; 
    [txtNSDate release]; 
    [txtNSArray release]; 
    [txtNSDictionary release]; 
    [txtInteger release]; 
    [txtFloat release]; 
    [txtDouble release]; 
    [super dealloc]; 

 
//保存数据到NSUserDefaults 
-(void)saveNSUserDefaults 

    NSString *myString = @"enuola"; 
    int myInteger = 100; 
    float myFloat = 50.0f; 
    double myDouble = 20.0; 
    NSDate *myDate = [NSDate date]; 
    NSArray *myArray = [NSArray arrayWithObjects:@"hello", @"world", nil]; 
    NSDictionary *myDictionary = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"enuo", @"20", nil] forKeys:[NSArray arrayWithObjects:@"name", @"age", nil]]; 
     
    //将上述数据全部存储到NSUserDefaults中 
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults]; 
    //存储时,除NSNumber类型使用对应的类型意外,其他的都是使用setObject:forKey: 
    [userDefaults setInteger:myInteger forKey:@"myInteger"]; 
    [userDefaults setFloat:myFloat forKey:@"myFloat"]; 
    [userDefaults setDouble:myDouble forKey:@"myDouble"]; 
     
    [userDefaults setObject:myString forKey:@"myString"]; 
    [userDefaults setObject:myDate forKey:@"myDate"]; 
    [userDefaults setObject:myArray forKey:@"myArray"]; 
    [userDefaults setObject:myDictionary forKey:@"myDictionary"]; 
     
    //这里建议同步存储到磁盘中,但是不是必须的 
    [userDefaults synchronize]; 
     

 
//从NSUserDefaults中读取数据 
-(void)readNSUserDefaults 

    NSUserDefaults *userDefaultes = [NSUserDefaults standardUserDefaults]; 
     
    //读取数据到各个label中 
    //读取整型int类型的数据 
    NSInteger myInteger = [userDefaultes integerForKey:@"myInteger"]; 
    txtInteger.text = [NSString stringWithFormat:@"%d",myInteger]; 
     
    //读取浮点型float类型的数据 
    float myFloat = [userDefaultes floatForKey:@"myFloat"]; 
    txtFloat.text = [NSString stringWithFormat:@"%f",myFloat]; 
     
    //读取double类型的数据 
    double myDouble = [userDefaultes doubleForKey:@"myDouble"]; 
    txtDouble.text = [NSString stringWithFormat:@"%f",myDouble]; 
     
    //读取NSString类型的数据 
    NSString *myString = [userDefaultes stringForKey:@"myString"]; 
    txtNSString.text = myString; 
     
    //读取NSDate日期类型的数据 
    NSDate *myDate = [userDefaultes valueForKey:@"myDate"]; 
    NSDateFormatter *df = [[NSDateFormatter alloc] init]; 
    [df setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; 
    txtNSDate.text = [NSString stringWithFormat:@"%@",[df stringFromDate:myDate]]; 
     
    //读取数组NSArray类型的数据 
    NSArray *myArray = [userDefaultes arrayForKey:@"myArray"]; 
    NSString *myArrayString = [[NSString alloc] init]; 
    for(NSString *str in myArray) 
    { 
        NSLog(@"str= %@",str); 
        myArrayString = [NSString stringWithFormat:@"%@  %@", myArrayString, str]; 
        [myArrayString stringByAppendingString:str]; 
//        [myArrayString stringByAppendingFormat:@"%@",str]; 
        NSLog(@"myArrayString=%@",myArrayString); 
    } 
    txtNSArray.text = myArrayString; 
     
    //读取字典类型NSDictionary类型的数据 
    NSDictionary *myDictionary = [userDefaultes dictionaryForKey:@"myDictionary"]; 
    NSString *myDicString = [NSString stringWithFormat:@"name:%@, age:%d",[myDictionary valueForKey:@"name"], [[myDictionary valueForKey:@"age"] integerValue]]; 
    txtNSDictionary.text = myDicString; 

 
@end 

 

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