IOS 数据存储详解及实例代码

沙盒根目录：NSString *home = NSHomeDirectory();
Documents：(2种方式)
1. 利用沙盒根目录拼接”Documents”字符串
//不建议采用，因为新版本的操作系统可能会修改目录名
NSString *home = NSHomeDirectory();
NSString *documents = [home stringByAppendingPathComponent:@"Documents"];
2. 利用NSSearchPathForDirectoriesInDomains函数
// NSUserDomainMask 代表从用户文件夹下找
// YES 代表展开路径中的波浪字符“~”
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, NO);
// 在iOS中，只有一个目录跟传入的参数匹配，所以这个集合里面只有一个元素
NSString *documents = [array objectAtIndex:0];
tmp：
NSString *tmp = NSTemporaryDirectory();
Library/Caches：
跟Documents类似的2种方法:
1. 利用沙盒根目录拼接”Caches”字符串
2. 利用NSSearchPathForDirectoriesInDomains函数(将函数的第2个参数改为：NSCachesDirectory即可)
Library/Preference：
通过NSUserDefaults类存取该目录下的设置信息

/ /获取路径
NSString *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
path = [path stringByAppendingPathComponent:@"save.plist"];
/ /将数据封装成字典
//不能存储对象
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:@"小黄" forKey:@"name"];
[dict setObject:@"12345678" forKey:@"phone"];
[dict setObject:@"24" forKey:@"age"];
// 将字典持久化到Documents/save.plist文件中
[dict writeToFile:path atomically:YES];

读取属性列表，恢复NSDictionary对象
// 读取Documents/save.plist的内容，实例化NSDictionary
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path];
NSLog(@"name:%@", [dict objectForKey:@"name"]);
NSLog(@"phone:%@", [dict objectForKey:@"phone"]);
NSLog(@"age:%@", [dict objectForKey:@"age"]);

//比如，保存用户名、字体大小、是否自动登录
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"mr.zk" forKey:@"username"];
[defaults setFloat:18.0f forKey:@"text_size"];
[defaults setBool:YES forKey:@"auto_login"];

//读取上次保存的设置
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *username = [defaults stringForKey:@"username"];
float textSize = [defaults floatForKey:@"text_size"];
BOOL autoLogin = [defaults boolForKey:@"auto_login"];

NSString *path = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
path = [path stringByAppendingPathComponent:@"array.data"];
NSArray *array = [NSArray arrayWithObjects:@”a”,@”b”,nil];
[NSKeyedArchiver archiveRootObject:array toFile:path];

NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

NSKeyedArchiver-归档Person对象（Person.h）
@interface Person : NSObject<NSCoding>
@property (nonatomic, strong) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, assign) float height;
@end

@implementation Person
- (void)encodeWithCoder:(NSCoder *)encoder {
  [encoder encodeObject:self.name forKey:@"name"];
  [encoder encodeInt:self.age forKey:@"age"];
  [encoder encodeFloat:self.height forKey:@"height"];
}
- (id)initWithCoder:(NSCoder *)decoder {
  self.name = [decoder decodeObjectForKey:@"name"];
  self.age = [decoder decodeIntForKey:@"age"];
  self.height = [decoder decodeFloatForKey:@"height"];
  return self;
}
@end

//归档(编码)
Person *person = [[[Person alloc] init] autorelease];
person.name = @"zk";
person.age = 24;
person.height = 1.73f;
[NSKeyedArchiver archiveRootObject:person toFile:path];
//恢复(解码)
Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

//归档（编码）
// 新建一块可变数据区
NSMutableData *data = [NSMutableData data];
// 将数据区连接到一个NSKeyedArchiver对象
NSKeyedArchiver *archiver = [[[NSKeyedArchiver alloc] initForWritingWithMutableData:data] autorelease];
// 开始存档对象，存档的数据都会存储到NSMutableData中
[archiver encodeObject:person1 forKey:@"person1"];
[archiver encodeObject:person2 forKey:@"person2"];
// 存档完毕(一定要调用这个方法)
[archiver finishEncoding];
// 将存档的数据写入文件
[data writeToFile:path atomically:YES];

//恢复（解码）
// 从文件中读取数据
NSData *data = [NSData dataWithContentsOfFile:path];
// 根据数据，解析成一个NSKeyedUnarchiver对象
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person *person1 = [unarchiver decodeObjectForKey:@"person1"];
Person *person2 = [unarchiver decodeObjectForKey:@"person2"];
// 恢复完毕
[unarchiver finishDecoding];