在iOS中的文本文件中寫入NSString而不會覆蓋數據

Question

我正在開發一個應用程序，我需要在不覆蓋現有數據的情況下寫入文件。我的代碼是：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; 

//creating a path 
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"file"]; 

//creating NSFileHandle and seeking for the end of file 
NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:appFile]; 
[fh seekToEndOfFile]; 

//appending data do the end of file 
NSString *dataString = @"Some Data"; 
NSData *data = [dataString dataUsingEncoding:NSASCIIStringEncoding]; 
[fh writeData:data]; 

代碼創建文件，但每次打開時，內容都會被覆蓋。一些解決方案

Answer 1

如果文件很大，這不是最佳解決方案。

您必須將文件內容讀入字符串。追加字符串與新數據。然後將字符串寫回文件。例如：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; 

//creating a path 
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"file"]; 

//Retriving contents of the file 
NSStringEncoding enco; 
NSMutableString *logStr = [NSMutableString stringWithContentsOfFile:appFile usedEncoding:&enco error:nil]; 

NSString *dataString = @"Some Data"; 
[logStr appendString:@"\n"]; 
[logStr appendString:dataString]; 
[logStr writeToFile:appFile atomically:NO encoding:NSUTF8StringEncoding error:nil];