剖析Objective-C持久化教程
剖析Objective-C持久化教程是本文要介绍的内容，很详细的讲解了Objective-C持久化的问题，不多说，我们来看内容。
当前需求
在做登录模块时，需要做登录的历史记录，存储本机所有登录的用户的用户名密码，以及登录策略如是否记住密码，是否自动登录等。具体实现之前，我认为这个需求看样子并不需要SQLite，因为登录用户不可能太多，而且存储的字段也就四个而已，估计用NSUserDefaults存一下数组就结了。
初遇困难
令我沮丧的是，这么一个明确的需求竟然一时半会都没有完成，用户登陆信息明明很简单的
Objective-c代码
@interface LoginUserInfo : NSObject
{
NSString *username_;
NSString *password_;
BOOL remember_;
BOOL autoLogin_;
}
@property (nonatomic, copy) NSString *username;
@property (nonatomic, copy) NSString *password;
@property (nonatomic, assign) BOOL remember;
@property (nonatomic, assign) BOOL autoLogin;
@end
@protocol LoginHistoryDelegate;
@interface LoginUserInfo : NSObject
{
NSString *username_;
NSString *password_;
BOOL remember_;
BOOL autoLogin_;
}
@property (nonatomic, copy) NSString *username;
@property (nonatomic, copy) NSString *password;
@property (nonatomic, assign) BOOL remember;
@property (nonatomic, assign) BOOL autoLogin;
@end
@protocol LoginHistoryDelegate; 存取的时候也很简单
Objective-c代码
// 增加一个用户要看是否是新用户，如果是新的就增加，否则要修改
- (void)addUser:(LoginUserInfo *)info
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSArray *list = [self getUserList];
NSArray *newList = nil;
if (list == nil)
{
newList = [NSArray arrayWithObject:info];
}
else
{
NSMutableArray *mutList = [[NSMutableArray alloc] initWithCapacity:[list count]+1];
[mutList addObject:info];
for (LoginUserInfo *user in list)
{
if (![[info username] isEqualToString:[user username]])
{
[mutList addObject:user];
}
}
newList = [mutList mutableCopy];
}
[defaults setObject:newList forKey:kUserHistoryKey];
[defaults synchronize];
[newList release];
}
- (NSArray *)getUserList
{
NSArray *objectArray = [[NSUserDefaults standardUserDefaults] objectForKey:kUserHistoryKey];
return objectArray;
}
// 增加一个用户要看是否是新用户，如果是新的就增加，否则要修改
- (void)addUser:(LoginUserInfo *)info
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSArray *list = [self getUserList];
NSArray *newList = nil;
if (list == nil)
{
newList = [NSArray arrayWithObject:info];
}
else
{
NSMutableArray *mutList = [[NSMutableArray alloc] initWithCapacity:[list count]+1];
[mutList addObject:info];
for (LoginUserInfo *user in list)
{
if (![[info username] isEqualToString:[user username]])
{
[mutList addObject:user];
}
}
newList = [mutList mutableCopy];
}
[defaults setObject:newList forKey:kUserHistoryKey];
[defaults synchronize];
[newList release];
}
- (NSArray *)getUserList
{
NSArray *objectArray = [[NSUserDefaults standardUserDefaults] objectForKey:kUserHistoryKey];
return objectArray;
} 但这样无论我怎么存储用户列表，在getUserList的时候获得的始终是nil。
各种尝试
难道是NSUserdefaults有问题么？我试了试在同个方法里改为存储普通的int，bool，甚至NSString都没问题，难道是因为没有存储数组么
Objective-c代码
NSArray *arr = [NSArray arrayWithObjects:@"xixi", @"haha", nil]; [[NSUserDefaults standardUserDefaults] setObject:arr forKey:@"Array"]; [[NSUserDefaults standardUserDefaults] synchronize]; NSArray *arr2 = [[NSUserDefaults standardUserDefaults] objectForKey:@"Array"]; NSString *s1 = [arr2 objectAtIndex:0]; NSLog(@"%@", s1); NSArray *arr = [NSArray arrayWithObjects:@"xixi", @"haha", nil]; [[NSUserDefaults standardUserDefaults] setObject:arr forKey:@"Array"]; [[NSUserDefaults standardUserDefaults] synchronize]; NSArray *arr2 = [[NSUserDefaults standardUserDefaults] objectForKey:@"Array"]; NSString *s1 = [arr2 objectAtIndex:0]; NSLog(@"%@", s1);
但此时仍然可以很顺利的显示出s1为xixi 没办法只好上网找资料了，这时注意到我存储的是自定义的结构，而和java的序列化类似，在序列化自定义类型的时候，必须要满足可序列化的一系列条件，甚至包括序列化的规则，就Objective-C而言，必须要实现NSCoding协议
Objective-c代码
- (void)encodeWithCoder:(NSCoder *)coder;
{
[coder encodeObject:username_ forKey:@"username"];
[coder encodeObject:password_ forKey:@"password"];
[coder encodeBool:remember_ forKey:@"remember"];
[coder encodeBool:autoLogin_ forKey:@"autologin"];
}
- (id)initWithCoder:(NSCoder *)coder;
{
self = [[LoginUserInfo alloc] init];
if (self != nil)
{
self.username = [coder decodeObjectForKey:@"username"];
self.password = [coder decodeObjectForKey:@"password"];
self.remember = [coder decodeBoolForKey:@"remember"];
self.autoLogin = [coder decodeBoolForKey:@"autologin"];
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder;
{
[coder encodeObject:username_ forKey:@"username"];
[coder encodeObject:password_ forKey:@"password"];
[coder encodeBool:remember_ forKey:@"remember"];
[coder encodeBool:autoLogin_ forKey:@"autologin"];
}
- (id)initWithCoder:(NSCoder *)coder;
{
self = [[LoginUserInfo alloc] init];
if (self != nil)
{
self.username = [coder decodeObjectForKey:@"username"];
self.password = [coder decodeObjectForKey:@"password"];
self.remember = [coder decodeBoolForKey:@"remember"];
self.autoLogin = [coder decodeBoolForKey:@"autologin"];
}
return self;
} 然后在存取的时候再加上序列化以及反序列化的代码
Objective-c代码
- (NSArray *)getUserList
{
NSArray *objectArray = nil;
NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:kUserHistoryKey];
if (data != nil)
{
NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:data];
if (oldSavedArray != nil)
objectArray = [[NSArray alloc] initWithArray:oldSavedArray];
// else
// objectArray = [[NSMutableArray alloc] init];
}
return objectArray;
}
// 增加一个用户要看是否是新用户，如果是新的就增加，否则要修改
- (void)addUser:(LoginUserInfo *)info
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSArray *list = [self getUserList];
NSArray *newList = nil;
if (list == nil)
{
newList = [NSArray arrayWithObject:info];
}
else
{
NSMutableArray *mutList = [[NSMutableArray alloc] initWithCapacity:[list count]+1];
[mutList addObject:info];
for (LoginUserInfo *user in list)
{
if (![[info username] isEqualToString:[user username]])
{
[mutList addObject:user];
}
}
newList = [mutList mutableCopy];
}
[defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:
newList] forKey:kUserHistoryKey];
[defaults synchronize];
[newList release];
}
- (NSArray *)getUserList
{
NSArray *objectArray = nil;
NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:kUserHistoryKey];
if (data != nil)
{
NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:data];
if (oldSavedArray != nil)
objectArray = [[NSArray alloc] initWithArray:oldSavedArray];
// else
// objectArray = [[NSMutableArray alloc] init];
}
return objectArray;
}
// 增加一个用户要看是否是新用户，如果是新的就增加，否则要修改
- (void)addUser:(LoginUserInfo *)info
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSArray *list = [self getUserList];
NSArray *newList = nil;
if (list == nil)
{
newList = [NSArray arrayWithObject:info];
}
else
{
NSMutableArray *mutList = [[NSMutableArray alloc] initWithCapacity:[list count]+1];
[mutList addObject:info];
for (LoginUserInfo *user in list)
{
if (![[info username] isEqualToString:[user username]])
{
[mutList addObject:user];
}
}
newList = [mutList mutableCopy];
}
[defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:
newList] forKey:kUserHistoryKey];
[defaults synchronize];
[newList release];
} 这样，总算可以持久化自定义结构了
和其他类似的语言一样，基础的序列化是个说大不大，说小不小的步骤，如果用纯c的话，就可以要完全自己去存储每个字节再读出每个字节然后解释出来，而现代语言基本上都做好了常见类型的持久化，包括更复杂的内置结构。
相关推荐
84407518 2012-07-16
87214552 2015-10-27
84407518 2016-01-25
89283517 2012-06-19
ObjectiveC 2012-06-14
fort0 2020-05-16
81570790 2020-04-16
86540698 2020-04-08
zhoutaifeng 2020-03-07
好好学习天天 2020-03-06
InterestSoul 2020-02-17
82467413 2019-12-31
81570790 2013-07-01
83254851 2013-08-29
84334052 2019-11-19
86540698 2019-11-19
84467715 2011-07-25
81731290 2014-03-22
85437811 2014-03-22