NSUserDefaults简介及使用

用户轻量级的数据持久化，主要用于保存用户程序的配置等信息，以便下次启动程序后能恢复上次的设置。

该数据实际上是以“键值对”形式保存的（类似于NSDictionary），因此我们需要通过key来读取或者保存数据（value）。

具体使用如下：

1、获取一个NSUserDefaults引用：

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

2、保存数据

[userDefaults setInteger:1 forKey:@"segment"];

[userDefaults synchronize];

3、读取数据

int i = [userDefaults integerForKey:@"segment"];

4、其他数据的存取

The NSUserDefaults class provides convenience methods for accessing common types such as floats, doubles, integers, Booleans, and URLs. A default object must be a property list, that is, an instance of (or for collections a combination of instances of): NSData,NSString, NSNumber, NSDate, NSArray, or NSDictionary. If you want to store any other type of object, you should typically archive it to create an instance of NSData. 

保存数据：

 

NSData *objColor = [NSKeyedArchiver archivedDataWithRootObject:[UIColor redColor]];

[[NSUserDefaults standardUserDefaults]setObject:objColor forKey:@"myColor"];

读取数据：

 

NSData *objColor = [[NSUserDefaults standardUserDefaults]objectForKey:@"myColor"];

 

UIColor *myColor = [NSKeyedUnarchiver unarchiveObjectWithData:objColor];

5、应用实例

-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

......

 

[cellSwitch setTag:indexPath.row];

[cellSwitch addTarget:self action:@selector(SwitchAction:) forControlEvents:UIControlEventValueChanged];

//retrieving cell switch value

NSUserDefaults *switchV = [NSUserDefaults standardUserDefaults];

int i= indexPath.row;

NSString *str = [[NSString alloc]initWithFormat:@"switch%d",i];

cellSwitch.on = ([switchV integerForKey:str]==1)?YES:NO;

 

......

 

 return cell;

}

 

-(void)SwitchAction:(id)sender

{

int i= [sender tag];

NSString *str = [[NSString alloc]initWithFormat:@"switch%d",i];

// save cell switch value

NSUserDefaults *switchV = [NSUserDefaults standardUserDefaults];

isOnOff = ([sender isOn] == 1)?1:0;

[switchV setInteger:isOnOff forKey:str];

 [switchV synchronize]; //调用synchronize函数将立即更新这些默认值。

  [str release];