IOS中NSUserDefaults的用法（轻量级本地数据存储）

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>

@inte易做图ce 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"

@inte易做图ce 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)shouldAutorotateToInte易做图ceOrientation:(UIInte易做图ceOrientation)inte易做图ceOrientation
{
    return (inte易做图ceOrientation != UIInte易做图ceOrientationPortraitUpsideDown);
}

- (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];
&n

补充：移动开发 , IOS ,