iPhone持久存储 [英] iPhone Persistent Storage

问题描述

我需要在执行应用程序时存储某些信息，并在应用程序启动时再次提取它。我试图使用GData存储在XML中，但没有成功。
我使用NSFileHandle它不给我一个错误，但它无法创建一个.txt文件读/写的目的。有没有任何其他方式在iPhone上存储和检索数据。下面是NSFileHandle的代码。

I need to store certain information while my application is executing and again fetch it at the time the application starts. I tried storing it in XML using GData but didn't succeed. I used the NSFileHandle it doesn't give me an error but it fails to create a .txt file for read / write purpose. Is there any other way of storing and retrieving the data on the iPhone. Below is my code for NSFileHandle.

NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"myFile.txt"];
//NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:@"file://localhost/Users/shraddha/Desktop/info.txt"];
NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:@"myFile.txt"];
[fh seekToEndOfFile];
NSData *data = [camName dataUsingEncoding:NSASCIIStringEncoding];
[fh writeData:data];
[fh closeFile];

阅读

NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"myFile.txt"];
//NSFileHandle *fh = [NSFileHandle fileHandleForReadingAtPath:@"file://localhost/Users/shraddha/Desktop/info.txt"];
NSFileHandle *fh = [NSFileHandle fileHandleForReadingAtPath:@"myFile.txt"];
if(fh == nil)
    return nil;
else
{
    NSData *data = [fh readDataOfLength:8];
    NSString *retStr = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
    return retStr;
}

推荐答案

到您可能没有权限的资源目录。尝试将代码的第一行改为指向文档目录：

You're trying to write to the resource directory which you probably don't have permission to do. Try changing the first line of your code to point to the document directory:

NSArray *savePaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSMutableString *savePath = [NSMutableString stringWithString:[savePaths objectAtIndex:0]];
[savePath appendString:@"/myFile.txt"];

此外，您不需要担心文件句柄。 NSData 能够写入磁盘：

Also, you don't need to worry about file handles. NSData is capable of writing itself to disk:

BOOL result = [data writeToFile:savePath atomically:YES];

这篇关于iPhone持久存储的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！