iOS开发之数据读写
iOS进阶
1：数据处理之数据读写
1):获取当前应用程序的沙盒根目录
NSString *rootPath = NSHomeDirectory();
NSLog(@"%@",rootPath);
rootPath就是根目录
然后将打印出来的文件目录右键单击选择services下的Reveal In Finder
2):
Documents：存储持久化文件数据
Library/Caches：存储缓存数据
Library/Preferences：存储应用的所有偏好设置
tmp：保存应用运行时所需的临时数据
3):定位当前应用程序的沙盒根目录
//1.Documents
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
NSLog(@"%@",docPath);
//2.library
NSString *libPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) firstObject];
NSLog(@"libPath is %@",libPath);
//3.library/Caches
NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSLog(@"cachesPath is %@",cachesPath);
//4.library/preferences 只能用拼接方法定位
NSString *prePath = [libPath stringByAppendingPathComponent:@"Preferences"];
NSLog(@"prePath is %@",prePath);
//5.tmp
NSString *tmpPath = NSTemporaryDirectory();
NSLog(@"tmpPath is %@",tmpPath);
4)：存储应用程序的偏好设置的类：NSUserDefaults
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults] ;
[defaults setObject:@"tang" forKey:@"name"] ;
//同步
[defaults synchronize] ;
NSLog(@"%@",[defaults objectForKey:@"name"]);
5）：简单对象的读写操作
只有四种简单的数据类型才能直接写入进文件
NSString NSDictionary NSData NSArray
第一步：获取沙盒下文件夹Documents的路径
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
第二步：创建需要写入的文件路径
NSString *filePath = [docPath stringByAppendingString:@"/text.txt"];
第三步：创建字符串对象
NSString *string = @"is副科级领导盖房了";
第四步：写入，四种简单的数据类型的写入方法差不多的
[string writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
第五步：读取字符串对象
NSString *resultStr = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
数组和字典可参照字符串对象的写入读取方法
*NSData对象的写入和读取(将图片存储)
第一步和第二步是一样的
第三步： UIImage *image = [UIImage imageNamed:@"0"];
第四步： NSData *data = UIImagePNGRepresentation(image);
第五步：写入
[data writeToFile:dataPath atomically:YES];
读取图片并在模拟器上显示:
NSData *resultData = [NSData dataWithContentsOfFile:dataPath];
UIImage *reImage = [UIImage imageWithData:resultData];
UIImageView *imageView = [[UIImageView alloc] initWithImage:reImage];
imageView.frame = self.view.bounds;
[self.view addSubview:imageView];
6）：在沙盒目录下创建文件
第一步：找到沙盒路径（caches）
//1.获取Documents目录
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
//2.创建文件路径
NSString *filePath = [docPath stringByAppendingString:@"/baobao.txt"];
//3.创建文件管理对象
NSFileManager *manager = [NSFileManager defaultManager];
//4.创建
[manager createFileAtPath:filePath contents:[@"sdfasdfs" dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];
NSLog(@"%@",filePath);
//计算文件或文件夹的大小
NSDictionary *dic = [manager attributesOfItemAtPath:filePath error:nil];
NSLog(@"%@",dic);
NSNumber *number = [dic objectForKey:NSFileSize];
NSLog(@"%@",number);
7）：创建文件夹和创建文件的核心代码差别在：
a：文件夹路径没有后缀名，文件有
b：文件管理器创建方法的不同
//2.创建文件夹的路径
NSString *filePath = [cachesPath stringByAppendingString:@"/text"];
//3.创建文件管理器对象
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:filePath withIntermediateDirectories:YES attributes:nil error:nil];
/*
在Documents文件夹下,创建一个文件夹(path),在该文件夹下创建一个文件(test.txt),将一个图片对象存入到该文件中,然后在Caches文件夹下创建一个文件夹名为"testDirectroy",将test.txt文件复制到这个文件夹下.
*/
- (void)moveFile {
//1.获取Documents目录
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
//2.创建文件夹路径
NSString *filePath = [docPath stringByAppendingString:@"/path"];
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:filePath withIntermediateDirectories:YES attributes:nil error:nil];
//3.创建文件路径
NSString *testPath = [filePath stringByAppendingString:@"/test.txt"];
[manager createFileAtPath:testPath contents:[@"aa" dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];
//4.写入图片
UIImage *image = [UIImage imageNamed:@"0"];
NSData *data = UIImagePNGRepresentation(image);
[data writeToFile:testPath atomically:YES];
//5.caches目录
NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
//6.创建文件夹testDirectroy
NSString *directoryPath = [cachesPath stringByAppendingPathComponent:@"testDirectroy"];
[manager createDirectoryAtPath:directoryPath withIntermediateDirectories:YES attributes:nil error:nil];
//7创建一个和documents中需要复制的文件同名的文件
NSString *desPath = [directoryPath stringByAppendingString:@"/test.txt"];
//8.复制时需要创建文件管理器
[manager copyItemAtPath:testPath toPath:desPath error:nil];
NSLog(@"%@",directoryPath);
}
/*
练习要求：
在Documents目录下创建一个文件text.txt
从文件的偏移量为3的时候开始追加内容1234
*/
- (void)addContent {
//1.得到Documents目录
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
//2.创建文件夹路径
NSString *filePath = [docPath stringByAppendingPathComponent:@"fiel"];
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:filePath withIntermediateDirectories:YES attributes:nil error:nil];
//3.创建文件路径
NSString *textPath = [filePath stringByAppendingPathComponent:@"/text.txt"];
[manager createFileAtPath:textPath contents:[@"hahahahahaha" dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];
//4.创建文件对接器
NSFileHandle *handle = [NSFileHandle fileHandleForUpdatingAtPath:textPath];
//此时文件在更新状态下，即可读也可写
[handle seekToFileOffset:3];
//5.开始在偏移量为3的地方写入字符串
[handle writeData:[@"1234" dataUsingEncoding:NSUTF8StringEncoding]];
[handle closeFile];
NSLog(@"%@",textPath);
}
//核心代码如下
//创建文件对接对象
NSFileHandle *handle = [NSFileHandle fileHandleForUpdatingAtPath:filePath];
//此时的文件对接对象 既可以读 也可以写
//将偏移量移动到3的位置
[handle seekToFileOffset:3];
//写入数据
[handle writeData:[@"1" dataUsingEncoding:NSUTF8StringEncoding]];
//执行完操作之后不要忘了关闭文件
[handle closeFile];
8）：复杂文件的归档和反归档（持久化操作）
//归档
- (void)archiver {
//1.创建person对象
Person *p1 = [[Person alloc] initWithName:@"tangxi" age:@"18"];
Person *p2 = [[Person alloc] initWithName:@"aren" age:@"20"];
//2.获取Documents目录
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filePath = [docPath stringByAppendingString:@"/haha.txt"];
//3.创建可变数据对象
NSMutableData *data = [NSMutableData data];
//4.创建归档类的对象
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
//5.将person对象归档
[archiver encodeObject:p1 forKey:@"person1"];
[archiver encodeObject:p2 forKey:@"person2"];
//6.结束归档
[archiver finishEncoding];//此时不管有几个对象没有被归档都会停止归档了
//7.将可变数据data写入创建的文件
[data writeToFile:filePath atomically:YES];
NSLog(@"%@",filePath);
}
//反归档
- (void)unarchiver {
//1.获取Documents目录
NSString *documents = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filePath = [documents stringByAppendingPathComponent:@"haha.txt"];
NSData *data = [NSData dataWithContentsOfFile:filePath];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person *person = [unarchiver decodeObjectForKey:@"person1"];
NSLog(@"name is %@, age is %@",person.name,person.age);
[unarchiver finishDecoding];
}
//还要创建一个模型对象Person,遵循NSCoding协议
实现两个协议方法:
- (instancetype)initWithName:(NSString *)name age:(NSString *)age {
self = [super init];
if (self) {
self.name = name;
self.age = age;
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:self.name forKey:@"name"];
[aCoder encodeObject:self.age forKey:@"age"];
}
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
NSString *name = [aDecoder decodeObjectForKey:@"name"];
NSString *age = [aDecoder decodeObjectForKey:@"age"];
return [self initWithName:name age:age];
}
//4.写入图片
UIImage *image = [UIImage imageNamed:@"0"];
NSData *data = UIImagePNGRepresentation(image);
[data writeToFile:testPath atomically:YES];
//4.创建文件对接器
NSFileHandle *handle = [NSFileHandle fileHandleForUpdatingAtPath:textPath];
//此时文件在更新状态下，即可读也可写
[handle seekToFileOffset:3];
//5.开始在偏移量为3的地方写入字符串
[handle writeData:[@"1234" dataUsingEncoding:NSUTF8StringEncoding]];
[handle closeFile];
NSLog(@"%@",textPath);
