iOS 本地数据持久化

本地数据持久化

1. 使用本地文件读写方式的本地数据持久化

/字符串的写入过程(实现文件内容拼接)/

//1. 获取源文件的路径

//1). 获取 Documents (存放永久存储的数据)文件夹路径

NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];

//2). 拼接上文件路径

NSString *filePath = [documentPath stringByAppendingPathComponent:@"sara.txt"];

//2. 获取源文件的内容

NSString *oldStr = [NSString stringWithContentOfFile:filePath encoding:NSUTF8StringEncoding error:nil];

//3.  将原有数据与新数据拼接在一起

NSString *newStr = [oldStr stringByAppendingFormat:@"%@", self.firstTF.text];

if (!newStr) {

newStr = self.firstTF.text;

}

//4. 将新的字符串写入文件

[newStr writeToFile:filePath automically:YES encoding:NSUTF8StringEncoding error:nil];//atomically 保证写入安全

/字符串的读取过程/

NSString *text = [NSString stringWithContentsO分File:filePath encoding:NSUTF8StringEncoding error:nil];

//让第二个输入框显示

self.secondTF.text = text;

//将数组写入文件

[stringArray writeToFile:filePath atomically:YES];//stringPath 是一个数组

//将数组从文件中读取出来

NSArray *dataArray = [NSArray arrayWithContentsOfFile:filePath];

self.firstTF.text = [dataArray firstObject];

self.secondTF.text = [dataArray lastObject];

//将字典写入文件

[dic writeToFile:filePath atomically:YES];

//将字典从文件中读取

NSDictionary *dic = [NSDictionary dictionaryWithContentsOfFile:filePath];

self.firstTF.text = dic[@"tf1"];

self.secondTF.text = dic[@"tf2"];

//将二进制数据写入文件

[data writeToFile:filePath atomically:YES];

//将二进制数据从文件中读取出来

NSData *data = [NSData dataWithContentOfFile:filePath];

2. 使用归档与反归档方式的本地数据持久化

//Contact类服从NSCoding 协议
//当对一个对象进行归档时, 自动调用该方法, 为该对象的实例变量进行归档操作
-(void)encodeWithCoder:(NSCoder *)aCoder {
//内部要对每一个实例变量进行归档
[aCoder encodeObject:_name forkey:@"name"];
[aCoder encodeObject:_gender forKey:@"gender"];
[aCoder encodeObject:@(_age) forKey:@"age"];
[aCoder encodeObject:_phone forKey:@"phone"];
}

//当对一个对象进行反归档时触发, 自动调用该方法, 为该对象的实例变量进行反归档操作
-(id)initWithCoder:(NSCoder *)aDecoder {
self = [super init];
if (self) {
self.name = [aDecoder decodeObjectForKey:@"name"];
self.gender = [aDecoder decodeObjectForKey:@"gender"];
self.age = [[aDecoder decodeObjectForKey:@"age"] integerValue];
self.phone = [aDecoder decodeObjectForKey:@"phone"];
}
return self;
}

//一. 归档
//将自定义的联系人对象contact进行本地数据持久化
//Contact *contact = [[Contact alloc] initWithName:@"Sara Burton" Gender:@"女" Age:18 phone:@"150xxxxxxxx"];
//1. 创建归档工具对象
NSMutableData *mData = [NSMutableData data];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:mData];
//2. 开始归档
[archiver encodeObject:contact forKey:@"contact"];
//3. 结束归档
[archiverfinishEncoding];// 一个结束归档就可以了
[contact release];
[archiver release];
//4. data 写入文件
[mData writeToFile:filePath atomically:YES];

//二. 反归档
//1. 从本地读取数据
NSData *data = [NSData dataWithContentsOfFile: filePath];
//2. 创建反归档工具
NSkeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
//3. 开始反归档
Contact *contact = [unarchiver decodeObjectForKey:@"key"];
//4. 结束反归档
[unarchiver finishDecoding];
//5. 释放
[unarchiver release];